Ethylene-based copolymers, lubricating oil compositions containing the same, and methods for making them

ABSTRACT

Provided are ethylene-based copolymers, methods of preparing the same, lubricating oil compositions including the same, methods for preparing such lubricating oil compositions, and end uses for such ethylene-based copolymers and lubricating oil compositions. The ethylene-based copolymers may include less than about 80 wt. % of units derived from ethylene and one or more alpha-olefin comonomers having 3 to 20 carbon atoms. The ethylene-based copolymers have a melting peak (Tm), as measured by DSC, of 80° C. or less, and a polydispersity index of about 2.8 or less. In some embodiments, the ethylene-based copolymers have an intramolecular composition distribution of about 50 wt. % or less and/or an intermolecular composition distribution of about 50 wt. % or less.

US PRIORITY

This application claims the priority to and the benefit from U.S. Ser.No. 61/173,528, filed on Apr. 28, 2009, and U.S. Ser. No. 61/173,501,filed on Apr. 28, 2009, and U.S. Ser. No. 12/569,009, filed on Sep. 29,2009, all of which are incorporated herein by reference in theirentirety.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Ser. No. 61/299,816, filed Jan. 29,2010, and U.S. Ser. No. 61/297,621, filed on Jan. 22, 2010, which areherein incorporated by reference in their entirety.

FIELD OF THE INVENTION

Provided are ethylene-based copolymers, methods of preparing the same,lubricating oil compositions including the same, methods for preparingsuch lubricating oil compositions, and end uses for such ethylene-basedcopolymers and lubricating oil compositions. More particularly, providedare ethylene-based copolymers and compositions containing the same,which are useful for increasing the thickening efficiency of lubricatingoils and related compositions.

BACKGROUND OF THE INVENTION

Many natural and synthetic compositions may benefit from additives thatmodify rheology. For example, lubricant oil formulations generallycontain viscosity index (VI) improvers derived from polyolefins thatmodify rheological behavior.

There have been many attempts to develop polyolefin additives that havea high thickening efficiency without raising the average ethylenecontent or the propensity to chain scission under shear.

However, conventional polyolefin additives suffer from unfavorablecharacteristics such as: (a) a high molecular weight fraction such thatthey are more affected by shear induced degradation of the molecularweight—such compositions have an unfavorable Thickening Efficiency(TE)/Shear Stability Index ratio (SSI) ratio in that they have a lowerTE for a given SSI; (b) preparation with metallocene catalysts in bulkpolymerization process, which provides process reactor heterogeneitythat leads to significant intermolecular composition and broadening ofpolydispersity index; (c) a blend of amorphous and semi crystallinepolyolefins that have a significant and predetermined intermolecularcompositional heterogeneity; and (d) polymerization conditions providingpolymers having significant long chain branching, which provides adiminished TE because they are topologically constrained from beingdispersed uniformly, at a molecular level, in solution.

Conventional VI improvers are taught in U.S. Pat. Nos. 4,540,753;4,804,794; 4,871,705; 5,151,204; 5,391,617; 5,446,221; 5,665,800;6,525,007; 6,589,920; and 7,053,153, which are each incorporated hereinby reference in their entirety.

Some conventional VI improvers, such as those described in U.S. Pat.Nos. 4,540,753 and 4,804,794, use an ultra narrow Polydipersity Index(PDI) composition. It is anticipated that these ultra narrow PDIpolymers lack a high molecular weight fraction so that they would beless affected by the shear induced degradation of the molecular weight.Such compositions are expected to have low SSI or a correspondingly highTE/SSI ratio.

Other conventional VI improvers, such as those described in U.S. Pat.Nos. 4,871,705 and 5,151,204, attempt to overcome structural limitationsby using a metallocene catalyst which provides a polyolefin having adistribution of molecular weights. However the use of the metallocenecatalysts in bulk polymerization process as described in theapplications indicates that the process reactor heterogeneity would leadto significant intermolecular composition and broadening of thepolydispersity index in the copolymer. Without being limited by theory,it is believed that the broader polydispersity index is due todifferences in the mixing and transport and equilibration of theconstituent monomers as well as differences in the temperature of thedifferent positions inside the polymerization reactor.

Another conventional VI improver includes a blend of amorphous and semicrystalline polyolefins as described in U.S. Pat. Nos. 5,391,617 and7,053,153. The combination of two such polymers attempts to provideincreased TE, shear stability, low temperature viscosity performance,and pour point. However, the design of the molecules have a significantand predetermined intermolecular compositional heterogeneity.

Still another conventional VI improver is described in U.S. Pat. Nos.6,525,007, 6,589,920, and 5,446,221. Such compositions are prepared witha single site metallocene catalyst in a solution polymerization. Howeverthe choice of the metallocene catalysts as well as the polymerizationconditions indicate that these polymers should have significant longchain branching as shown in U.S. Pat. No. 5,665,800. Such long chainbranched polymers have a diminished TE compared to their linearanalogues since they are topologically constrained from being disperseduniformly, at a molecular level, in solution.

There remains a need for VI improving compositions that promote thefollowing in lubricant oils, while maintaining a low ethylene content:(a) a more constant viscosity over a broad range of temperatures; (b)improved TE; and (c) improved ratio of the TE to the SSI.

SUMMARY OF THE INVENTION

Provided are ethylene-based copolymers, methods of preparing the same,lubricating oil compositions including the same, methods for preparingsuch lubricating oil compositions, and end uses for such ethylene-basedcopolymers and lubricating oil compositions.

Ethylene-based copolymers include less than about 80 wt. % of unitsderived from ethylene and one or more alpha-olefin comonomers having 3to 20 carbon atoms. The ethylene-based copolymer has a melting peak(Tm), as measured by DSC, of 80° C. or less, a polydispersity index ofabout 2.8 or less. In some embodiments, the ethylene-based copolymershave an intermolecular composition distribution of about 50 wt. % orless. In other embodiments the ethylene-based copolymers have anintramolecular composition distribution of about 50 wt. % or less. Insome embodiments, the ethylene-based copolymers have an intramolecularcomposition distribution of about 40 wt. % or less and/or anintermolecular composition distribution of about 40 wt. % or less.

The ethylene-based copolymers are useful in rheology modifyingcompositions, such as viscosity modifiers in oil and polymercompositions, e.g., lubricating oil compositions.

Lubricating oil compositions are composed of a lubricating oil base andthe ethylene-based copolymer. When added to lubricant oils,ethylene-based copolymers promote a more constant viscosity over a broadrange of temperatures, for example, operating conditions of combustionengines. Such improvements are achieved while maintaining a low ethylenecontent. At substantially similar composition and molecular weight, thepresent lubricating oil compositions exhibit unexpectedly improvedphysical properties, such as higher TE, and better ratio of the TE tothe SSI compared to conventional viscosity modifiers.

Methods of preparing ethylene-based copolymers include utilizing ametallocene catalyst in a synthesis process designed to control thedistribution of monomers and polymer chain architecture to form uniformand/or linear polymers. The resulting polymers exhibit high TE and ahigh ratio of TE/SSI. Further, the choice of the alpha olefin comonomerwill affect other properties of the ethylene-based copolymer such assolubility parameter, TE, and SSI, but these secondary effects areovershadowed by the fundamental change and the control, due to theconstruction of the ethylene-based copolymer to be uniform and/orlinear. Without being limited by theory, it is believed that theaddition of alpha olefins may, in addition, lead to a further degree ofcontrol in the polymer chain such that the level of crystallinity willbe diminished and thus the fluidity of the solutions containing thepolymers will be enhanced.

DESCRIPTION OF THE FIGURES

FIG. 1 is graph of TE versus ethylene weight percent for exemplarycompositions and a conventional composition. This graph refers toexperiments in “Group I Examples”.

FIG. 2 is a graph of Anton Parr rheology data versus temperature showingthe resistance to low temperature viscosity increase for exemplarycompositions and conventional compositions. This graph refers toexperiments in “Group I Examples”.

FIG. 3 is a graph of crystallinity weight percent versus ethylene weightpercent for exemplary compositions and conventional compositions. Thisgraph refers to experiments in “Group II Examples”.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

Ethylene-based copolymers include less than about 80 wt. % of unitsderived from ethylene and alpha olefin comonomers having 3 to 20 carbonatoms. As used herein “ethylene-based copolymer” means a copolymercomposed of a substantial quantity of ethylene monomer, e.g., greaterthan 30 wt. % ethylene, and one or more comonomers. Thus, ethylene-basedcopolymers may be composed of more units derived from alpha olefincomonomer by weight compared to units derived from ethylene. As usedherein the term “copolymer” is any polymer having two or more monomers.

Suitable comonomers include propylene and α-olefins, such as C₄-C₂₀α-olefins and preferably propylene and C₄-C₁₂ α-olefins. The α-olefincomonomer can be linear or branched, and two or more comonomers can beused, if desired. Thus, reference herein to “an alpha-olefin comonomer”includes one, two, or more alpha-olefin comonomers. Examples of suitablecomonomers include propylene, linear C₄-C₁₂ α-olefins, and α-olefinshaving one or more C₁-C₃ alkyl branches. Specific examples include:propylene; 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene;1-pentene; 1-pentene with one or more methyl, ethyl, or propylsubstituents; 1-hexene with one or more methyl, ethyl, or propylsubstituents; 1-heptene with one or more methyl, ethyl or propylsubstituents; 1-octene with one or more methyl, ethyl, or propylsubstituents; 1-nonene with one or more methyl, ethyl or propylsubstituents; ethyl, methyl, or dimethyl-substituted 1-decene, or1-dodecene. Preferred comonomers include: propylene; 1-butene;1-pentene; 3-methyl-1-butene; 1-hexene; 3-methyl-1-pentene;4-methyl-1-pentene; 3,3-dimethyl-1-butene; 1-heptene; 1-hexene with amethyl substituent on any of C₃-C₅; 1-pentene with two methylsubstituents in any stoichiometrically acceptable combination on C₃ orC₄; 3-ethyl-1-pentene; 1-octene; 1-pentene with a methyl substituent onany of C₃ or C₄; 1-hexene with two methyl substituents in anystoichiometrically acceptable combination on C₃-C₅; 1-pentene with threemethyl substituents in any stoichiometrically acceptable combination onC₃ or C₄; 1-hexene with an ethyl substituent on C₃ or C₄; 1-pentene withan ethyl substituent on C₃ and a methyl substituent in astoichiometrically acceptable position on C₃ or C₄; 1-decene; 1-nonene;1-nonene with a methyl substituent on any of C₃-C₉; 1-octene with twomethyl substituents in any stoichiometrically acceptable combination onC₃-C₇; 1-heptene with three methyl substituents in anystoichiometrically acceptable combination on C₃-C₆; 1-octene with anethyl substituent on any of C₃-C₇; 1-hexene with two ethyl substituentsin any stoichiometrically acceptable combination on C₃ or C₄; and1-dodecene.

Preferred alpha olefin comonomers are propylene, butene, hexene, oroctene. A more preferred alpha olefin comonomer is propylene. Anotherpreferred olefin comonomer is 1 butene. Combinations propylene andbutene are contemplated.

Other suitable comonomers include internal olefins. Preferred internalolefins are cis 2-butene and trans 2-butene. Other internal olefins arecontemplated.

Other suitable comonomers include polyenes. The term “polyene” as usedherein is meant to include monomers having two or more unsaturations;i.e., dienes, trienes, etc. Polyenes particularly useful as co-monomersare non-conjugated dienes, preferably are straight chain, hydrocarbondi-olefins or cycloalkenyl-substituted alkenes, having about 6 to about15 carbon atoms, for example: (a) straight chain acyclic dienes, such as1,4-hexadiene and 1,6-octadiene; (b) branched chain acyclic dienes, suchas 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6; (c) single ring alicyclicdienes, such as 1,4-cyclohexadiene, 1,5-cyclo-octadiene, and1,7-cyclododecadiene; (d) multi-ring alicyclic fused and bridged ringdienes, such as tetrahydroindene, norbornadiene,methyl-tetrahydroindene, dicyclopentadiene (DCPD),bicyclo-(2.2.1)-hepta-2,5-diene, alkenyl, alkylidene, cycloalkenyl, andcycloalkylidene norbornenes, such as 5-methylene-2-norbornene (MNB),5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, and5-vinyl-2-norbornene (VNB); and (e) cycloalkenyl-substituted alkenes,such as vinyl cyclohexene, allyl cyclohexene, vinyl cyclooctene, 4-vinylcyclohexene, allyl cyclodecene, and vinyl cyclododecene. Of thenon-conjugated dienes typically used, the preferred dienes aredicyclopentadiene (DCPD), 1,4-hexadiene, 1,6-octadiene,5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,5-methylene-2-norbornene, 5-ethylidene-2-norbornene (ENB), andtetracyclo (Δ-11,12) 5,8 dodecene. Note that throughout this applicationthe terms “polyene”, “non-conjugated diene”, and “diene” are usedinterchangeably. It is preferred to use dienes which do not lead to theformation of long chain branches. For successful use as VI improver non-or lowly branched polymer chains are preferred. Other polyenes that canbe used include cyclopentadiene and octatetra-ene.

Ethylene-based copolymers include from about 30 wt. % to about 80 wt. %ethylene comonomer. Preferably, ethylene-based copolymers include lessthan about 70 wt. % ethylene comonomer, or less than about 60 wt. %ethylene comonomer. In some embodiments, ethylene-based copolymersinclude from about 40 wt. % to about 80 wt. % ethylene comonomer or fromabout 45 wt. % to about 70 wt. % ethylene comonomer. Ethylene-basedcopolymers include from about 42 wt. % to about 78 wt. % ethylenecomonomer, or from about 45 wt. % to about 76 wt. % ethylene comonomer,or from about 48 wt. % to about 76 wt. % ethylene comonomer, or fromabout 48 wt. % to about 74 wt. % ethylene comonomer, or from about 50wt. % to about 72 wt. % ethylene comonomer, or from about 45 wt. % toabout 50 wt. % ethylene comonomer.

Ethylene-based copolymers exhibit one or more of the followingproperties or combinations of the following properties:

-   -   A weight-average molecular weight (Mw) in terms of polystyrene,        as measured by GPC, in the range of about 30,000 to about        800,000. More preferably, the weight average Mw is from about        50,000 to about 600,000 or from about 80,000 to about 400,000.        Even more preferably, the weight average Mw is from about 10,000        to about 300,000.    -   A number-average molecular weight (Mn), as measured by GPC, of        from about 10,000 to about 400,000, or in the range of about        20,000 to about 300,000, or in the range of about 30,000 to        about 200,000.    -   A weight-average molecular weight to number-average molecular        weight (Mw/Mn) of about 5.0 or less, or about 4.0 or less, or        3.0 or less, or 2.2 or less. In one or more embodiments, the        Mw/Mn is from about 1.0 to about 3.0, or from about 1.5 to about        2.5.    -   A PDI of less than about 2.8, or less than about 2.6, or less        than about 2.4, preferably less than about 2.3 and more        preferably less than about 2.2 as measured by GPC.    -   Substantially no crystallinity as evidenced by the absence of a        melting peak as measured by DSC    -   A melting point (Tm), if present, as measured by DSC, of about        110° C. or less, or about 100° C. or less, or about 90° C. or        less, or about 80° C. or less, or about 70° C. or less, or about        65° C. or less.    -   A heat of fusion on a first melt of from about 0 to about 60        J/g, or from about 0 to about 50 J/g, or from about 0.001 to        about 40 J/g, or from about 0.001 to about 35 J/g, or less than        about 30 J/g, or less than about 20 J/g, or less than about 15        J/g, or about 10 J/g.    -   Intermolecular uniformity, such that the ethylene-based        copolymers have an intermolecular composition distribution of        about 50 wt. % or less, or 40 wt. % or less, or 30 wt. % or        less, or 20 wt. % or less, or 15 wt. % or less, or 10 wt. % or        less, or 5 wt. % or less. In some embodiments, at least 50 wt.        %, at least 60 wt. %, at least 80 wt. %, at least 90 wt. %, or        100 wt. % of the ethylene-based copolymers have an        intermolecular composition distribution of about 50 wt. % or        less, or 40 wt. % or less, or 30 wt. % or less, or 20 wt. % or        less, or 15 wt. % or less, or 10 wt. % or less, or 5 wt. % or        less.    -   Intramolecular uniformity, such that the ethylene-based        copolymers have an intramolecular composition distribution of        about 50 wt. % or less, or 40 wt. % or less, or 30 wt. % or        less, or 20 wt. % or less, or 15 wt. % or less, or 10 wt. % or        less, or 5 wt. % or less. In some embodiments, at least 50 wt.        %, at least 60 wt. %, at least 80 wt. %, at least 90 wt. %, or        100 wt. % of the ethylene-based copolymers have an        intramolecular composition distribution of about 50 wt. % or        less, or 40 wt. % or less, or 30 wt. % or less, or 20 wt. % or        less, or 15 wt. % or less, or 10 wt. % or less, or 5 wt. % or        less.    -   A substantially linear structure as having no greater than one        branch point, pendant with a carbon chain larger than 19 carbon        atoms, per 200 carbon atoms along the polymer backbone. In some        embodiments, substantially linear ethylene-based copolymers are        further characterized as having:        -   (a) less than 1 branch point, pendent with a carbon chain            longer than 10 carbon atoms, per 200 carbon atoms along a            polymer backbone, or less than 1 branch point per 300 carbon            atoms, or less than 1 branch point per 500 carbon atoms and            preferably less than 1 branch point per 1000 carbon atoms,            notwithstanding the presence of branch points due to            incorporation of the comonomer; and/or        -   (b) no greater than one branch point, pendant with a carbon            chain larger than 19 carbon atoms per 300 carbon atoms, or            no greater than one per 500 carbon atoms, or no greater one            per 1000 carbon atoms, or no greater than one per 2000            carbon atoms.

Ranges from any of the lower limits to any of the upper limits arecontemplated by the inventors and are within the scope of the presentdescription.

As used herein, intermolecular composition distribution (InterCD orintermolecular CD), i.e., a measure of compositional heterogeneity,defines the compositional variation, in terms of ethylene content, amongpolymer chains. It is expressed as the minimum deviation, analogous to astandard deviation, in terms of weight percent ethylene from the averageethylene composition for a given copolymer sample needed to include agiven weight percent of the total copolymer sample which is obtained byexcluding equal weight fractions from both ends of the distribution. Thedeviation need not be symmetrical. When expressed as a single number,for example, an intermolecular composition distribution of 15 wt. %shall mean the larger of the positive or negative deviations.

At 50 wt. % intermolecular composition distribution the measurement issimilar to conventional Composition Distribution Breadth Index (CDBI).As used herein CDBI is defined in U.S. Pat. No. 5,382,630 which ishereby incorporated by reference. CDBI is defined as the weight percentof the copolymer molecules having a comonomer content within 50% of themedian total molar comonomer content. The CDBI of a copolymer is readilydetermined utilizing well known techniques for isolating individualfractions of a sample of the copolymer. One such technique isTemperature Rising Elution Fraction (TREF), as described in Wild, etal., Journal of Polymer Science: Polymer Physics Edition, Vol. 20, Issue3, pp. 441-455 (1982) and U.S. Pat. No. 5,008,204, which areincorporated herein by reference.

As used herein intramolecular composition distribution (IntraCD orintramolecular CD) is similar to intermolecular compositiondistribution; however, IntraCD measures the compositional variation, interms of ethylene, within a copolymer chain. Intramolecular-CD isexpressed as the ratio of alpha-olefin to ethylene along the segments ofthe same polymer chain. InterCD and IntraCD are described in U.S. Pat.No. 4,959,436, which is hereby incorporated by reference.

Compositional heterogeneity both intermolecular-CD and intramolecular-CDare determined by carbon-13 NMR. Conventional techniques for measuringintermolecular-CD and intramolecular-CD are described in H. N. Cheng etal., Macromolecules, entitled “Carbon-13 NMR analysis of compositionalheterogeneity in ethylene-propylene copolymers”, 24 (8), pp 1724-1726,(1991), and in the publication Macromolecules, C. Cozewith, entitled“Interpretation of carbon-13 NMR sequence distribution forethylene-propylene copolymers made with heterogeneous catalysts”, 20(6), pp 1237-1244, (1987), each of which is herein incorporated byreference in its entirety.

Generally, conventional carbon-13 NMR measurement of diad and triaddistribution is used to characterize the ethylene-based copolymer. Anyconventional technique for measuring carbon-13 NMR may be utilized. Forexample, ethylene-based copolymer samples are dissolved in a solvent,e.g., trichlorobenzene at 4.5 wt. % concentration. The Carbon-13 NMRspectra are obtained at elevated temperature, e.g., 140° C., on a NMRspectrometer at 100 MHz. An exemplary spectrometer is a pulsed Fouriertransform Varian XL-400 NMR spectrometer. Deuteriated o-dichlorobenzeneis placed in a coaxial tube to maintain an internal lock signal. Thefollowing instrument conditions are utilized: pulse angle, 75°; pulsedelay, 25 s; acquisition time, 0.5 s, sweep width, 16000 Hz. Thecarbob-13 NMR peak area measurements were determined by spectralintegration. Diad and triad concentrations were calculated from theequations presented in Kakugo et al., Macromolecules, 15, pp. 1150-1152,(1982), which is herein incorporated by reference in its entirety. Thediad and triad concentrations were then normalized to give a molefraction distribution. Polymer composition was calculated form themethane peaks, the methylene peaks, and the diad balance. These valuesmay be considered individually or an average of the three values may beutilized. Unless stated otherwise, this application utilizes an averageof these three values. The results are then compared to conventionalmodel equations as disclosed in the above references.

One aspect of these measurements involves the determination of thereactivity ratios (r₁r₂) of the polymerization system for theethylene-based polymers. Polymers which have a compositionalheterogeneity, either intramolecular or intermolecular, have a muchlarger reactivity ratio than the polymers which have only a small ornegligible amount.

Without being limited to theory or one method of calculation, it isbelieved that an one exemplary model for, so called idealcopolymerizations, is described by the terminal copolymerization model:m=M(r ₁ M+1)/(r ₂ +M)  (1)Wherein r₁ and r₂ are the reactivity ratios, m is the ratio of monomersin the copolymer, m₁/m₂, M is the ratio of monomers in the reactor,M₁/M₂, and the diad and triad concentrations follow first order Markovstatistics. For this model, nine equations are derived that related tothe diad and triad concentrations P₁₂ and P₂₁, the probability ofpropylene adding to an ethylene-ended chain, and the probability ofpropylene adding to a propylene-ended chain, respectively. Thus a fit ofcarbon-13 NMR data to these equations yields P₁₂ and P₂₁ as the modelparameters from which r₁ and r₂ can be obtained from the relationships:r ₁ M=(1−P ₁₂)/P ₁₂r ₂ /M=(1−P ₂₁)/P ₂₁

The corresponding equations for random copolymerizations with r₁r₂=1 canalso be used to simplify equation (1), above, to m=r₁M. The ethylenefraction in the polymer, E, is equal to 1-P₁₂. This allows the diad andtriad equations to be written in terms of polymer composition:EE=E ²EE=2E(1−E)PP=(1−E)²EEE=E ³EEP=2E ²(1−E)EPE=E ²(1−E)PEP=E(1−E)²PPE=2E(1−E)²PPP=(1−E)³

Variations and extensions of these equations are provided in thereferences incorporated above, including use of catalysts with differentactive sites, equations for estimating the number of catalyst speciespresent, or complex models such as those with three or more speciespresent, etc.

From these modeling equations, and those equations presented by C.Cozewith et al., Macromolecules, 4, pp. 482-489, (1971), which is hereinincorporated by reference in its entirety, the average values of r₁, r₂,and r₁r₂ arising from the copolymerization kinetics are given by:r ₁ =(Σr _(1i) f _(i) /G _(i))/(Σf _(i) /G _(i))r ₂ =(Σr _(2i) f _(i) /G _(i))/(Σf _(i) /G _(i))r ₁ r ₂ =(Σr _(1i) f _(i) /G _(i))(Σr _(2i) f _(i) /G _(i))/(Σf _(i) /G_(i))²

-   -   where G_(i)=r_(1i)M±2+r_(2i) /M

These equations and the models presented in the references cited abovemay be utilized by those skilled in the art to characterize theethylene-based copolymer composition distribution.

Techniques for measuring intramolecular-CD are found in Randel, JamesC., Macromolecules, 11(1), pp. 33-36, (1978); Cheng, H. N.,Macromolecules, 17(10), pp. 1950-1955, (1984); Ray, G. Joseph et al.,Macromolecules, 10(4), pp. 773-778, (1977); and U.S. Pat. No. 7,232,871,each of which is incorporated by reference in its entirety. Suchtechniques are readily known to those skilled in the art of analyzingand characterizing olefin polymers.

As used herein, Polydispersity Index (PDI), also known as molecularweight distribution (MWD), is a measure of the range of molecularweights within a given copolymer sample. It is characterized in terms ofat least one of the ratios of weight average to number average molecularweight, Mw/Mn.

Ethylene-based copolymers are useful as rheology modifying compositions.Accordingly, ethylene-based polymer compositions are used independentlyto modify rheology in hydrocarbon compositions, such as lubricatingoils. Alternatively, ethylene-based copolymers are combined withconventional additives to modify the rheology of hydrocarboncompositions. As described below, conventional additives, includeolefin-based additives, or mineral based additives, each of which isknow to those skilled in the art.

Higher concentrations of additives may be utilized to form masterbatchesof ethylene-based copolymers. Such masterbatches may include minoramounts of ethylene-based copolymers, such as from about 1.0 wt. % toabout 10 wt. % or more than 10 wt. % of ethylene-based copolymer.Exemplary masterbatches also include larger quantities of ethylene-basedcopolymer such as from about 50 wt. % to about 99 wt. % ethylene-basedcopolymers.

Ethylene-based copolymers include a single reactor-grade polymer, aninterpolymer, i.e., a reactor blend of one or more copolymers, or apost-reactor blend of one or more copolymer, i.e., either via blendingpellets or otherwise.

In one or more embodiments, the ethylene-based copolymers are grafted,contain a grafted ethylene-based copolymer, or are part of a compositionthat is grafted. Typical grafting techniques are known to those skilledin the art, such techniques using maleic acid. In one or moreembodiments, the ethylene-based copolymers are derivatized.

In one embodiment, the ethylene-based copolymer is composed of fromabout 35 wt. % to about 80 wt. % of units derived from ethylene, basedon the weight of the ethylene-based copolymer, and an α-olefin comonomerhaving 3 to 20 carbon atoms, wherein the ethylene-based copolymer has:(a) a melting point (Tm), as measured by DSC, of 80° C. or less, amelting peak (Tm), as measured by DSC, of 80° C. or less; (b) apolydispersity index of about 2.6 or less; and (c) an intramolecularcomposition distribution of about 30 wt. % or less.

In one embodiment, the ethylene-based copolymer is composed of fromabout 40 wt. % to about 60 wt. % of units derived from ethylene, basedon the weight of the ethylene-based copolymer, and at least 1.0 wt. %α-olefin comonomer having 3 to 20 carbon atoms, wherein theethylene-based copolymer has: (a) a melting point (Tm), as measured byDSC, of 80° C. or less, a melting peak (Tm), as measured by DSC, of 80°C. or less; (b) a polydispersity index of about 2.4 or less; and (c) anintramolecular composition distribution of about 20 wt. % or less.

In one embodiment, the ethylene-based copolymer is composed of fromabout 40 wt. % to about 60 wt. % of units derived from ethylene, basedon the weight of the ethylene-based copolymer, and at least 1.0 wt. %α-olefin comonomer having 3 to 20 carbon atoms, wherein theethylene-based copolymer has: (a) a melting point (Tm), as measured byDSC, of 80° C. or less, a melting peak (Tm), as measured by DSC, of 80°C. or less; (b) a polydispersity index of about 2.4 or less; (c) anintramolecular composition distribution of about 15 wt. % or less; and(d) an intermolecular composition distribution of about 15 wt. % orless.

In each of the intermolecular and intramolecular compositiondistribution values disclosed herein, at least 50 wt. %, preferably atleast 60 wt. %, at least 80 wt. %, at least 90 wt. %, and mostpreferably 100 wt. % of the ethylene-based copolymers have thedistribution values recited.

In one or more embodiments, two or more ethylene-based copolymers arecombined to form compositionally disperse polymeric compositions.Compositionally disperse polymeric compositions are taught in U.S.Provisional Patent App. No. 61/173,501, incorporated herein by referencein its entirety. Accordingly, the ethylene-based copolymer is blendedwith other components, e.g., additional ethylene-based polymers and/oradditives, to form compositionally disperse polymeric compositions.

In one or more embodiments, two or more ethylene-based copolymers arecombined to form crystallinity dispersed polymeric compositions.Crystallinity dispersed polymeric compositions are taught in U.S.Provisional Patent App. No. 61/173,501. Accordingly, the ethylene-basedcopolymer is blended with other components, e.g., additionalethylene-based polymers and/or additives, to form compositionallydisperse polymeric compositions.

In one or more embodiments, the ethylene-based copolymer issubstantially, or completely amorphous. Substantially amorphous as usedherein means less than about 2.0 wt. % crystallinity. Preferably,amorphous ethylene-based copolymers have less than about 1.5 wt. %crystallinity, or less than about 1.0 wt. % crystallinity, or less thanabout 0.5 wt. % crystallinity, or less than 0.1 wt. % crystallinity. Ina preferred embodiment, the amorphous ethylene-based copolymer does notexhibit a melt peak as measured by DSC.

Exemplary amorphous ethylene-based copolymers are composed of from about35 wt. % to about 60 wt. % units derived from ethylene, and at least 1.0wt. % or more of an α-olefin comonomer having 3 to 20 carbon atoms,based on the weight of the ethylene-based copolymer, wherein theethylene-based copolymer is substantially amorphous, and has apolydispersity index of about 2.6 or less, or about 2.4 or less, orabout 2.2 or less.

In other embodiments of such “amorphous” ethylene-based copolymers, theethylene-based copolymer is composed of from about 35 wt. % to about 50wt. % unit derived from ethylene, or from about 40 wt. % to about 50 wt.% unit derived from ethylene, or from about 45 wt. % to about 50 wt. %unit derived from ethylene, or from about 45 wt. % to about 49 wt. %unit derived from ethylene, based on the weight of the ethylene-basedcopolymer.

Preferably, such amorphous ethylene-based copolymers exhibit nosubstantial melting peak or no melting peak when measured by DSC.

In one or more embodiments, the amorphous ethylene-based copolymer havean MFR (230° C., 2.16 kg) of from about 3 to about 10 kg/10 min.

In one or more embodiments, the amorphous ethylene-based copolymer hasan intramolecular composition distribution of about 15 wt. % or less, oran intermolecular composition distribution of about 15 wt. % or less, orboth an intra-CD and inter-CD of 15 wt. % or less.

Ethylene-based copolymers, as described herein, are useful as blendcomponents in conventional polymer compositions, e.g., ethylenehomopolymers or copolymers, or propylene homopolymers or copolymers, andin thermoplastic vulcanizates (TPV). Further, such ethylene-basedcopolymers are useful as additives or primary components in moldedarticles, extrudates, films, e.g., blown films, etc., woven and nonwovenfabrics, adhesives, and conventional elastomer applications.

Methods For Preparing Ethylene-Based Copolymers

Methods for making ethylene-based copolymers include a step forcopolymerizing an ethylene and an alpha-olefin. Preferably, methods ofpreparing ethylene-based polymers include the steps of copolymerizingethylene and a first comonomer in the presence of a first metallocenecatalyst in a first polymerization reaction zone under firstpolymerization conditions to produce a first effluent comprising a firstethylene-based copolymer.

Methods of preparing ethylene-based copolymers include the steps ofcopolymerizing ethylene and one or more comonomer in the presence of oneor more metallocene catalysts in one or more polymerization reactionzones under polymerization conditions to produce one or more effluents,respectively, which each comprise an ethylene-based copolymer. Thus,such methods contemplate the use of two or more reactors to prepare asingle ethylene-based copolymer, or two or more reactors that are usedto prepare two or more ethylene-based copolymers that are blended duringor after polymerization.

Conventional processes have prepared VI improving polymers by bulkpolymerizations or multi-step processes. Such complicated oruneconomical processes may be used to prepare the present ethylene-basedcopolymers. However, it is preferred to use simplified process asdescribed herein.

Catalyst System

The term “catalyst system” means a catalyst precursor/activator pair.When “catalyst system” is used to describe such a pair beforeactivation, it means the unactivated catalyst (precatalyst) togetherwith an activator and, optionally, a co-activator. When it is used todescribe such a pair after activation, it means the activated catalystand the activator or other charge-balancing moiety. The transition metalcompound or complex may be neutral as in a precatalyst, or a chargedspecies with a counter ion as in an activated catalyst system. The term“catalyst-system” can also include more than one catalyst precursor andor more than one activator and optionally a co-activator. Likewise, theterm “catalyst-system” can also include more than one activated catalystand one or more activator or other charge-balancing moiety, andoptionally a co-activator.

Catalyst precursor is also often referred to as precatalyst, catalyst,catalyst compound, transition metal compound, or transition metalcomplex. These terms are used interchangeably. Activator and cocatalyst(or co-catalyst) are also used interchangeably. A scavenger is acompound that is typically added to facilitate polymerization byscavenging impurities. Some scavengers may also act as activators andmay be referred to as co-activators. A co-activator that is not ascavenger may also be used in conjunction with an activator in order toform an active catalyst. In some embodiments, a co-activator can bepre-mixed with the transition metal compound to form an alkylatedtransition metal compound.

An activator or cocatalyst is a compound or mixture of compounds capableof activating a precatalyst to form an activated catalyst. The activatorcan be a neutral compound (Lewis acid activator) such astris-perfluorophenyl boron or tris-perfluorophenyl aluminium, or anionic compound (ionic activator) such as dimethylaniliniumtetrakis-perfluorophenyl borate or dimethylaniliniumtetrakis-perfluoronaphthyl borate. Activators are also commonly referredto as non-coordinating anion activators or ionic activators owing to thecommonly held belief by those skilled in the art, that the reaction ofthe activator with the precatalyst forms a cationic metal complex and ananionic non-coordinating or weakly coordinating anion.

Catalyst

Although any conventional catalyst may be used to prepare ethylene-basedcopolymers, preferably polymerization takes place in the presence of ametallocene catalyst. The term “metallocene”, “metallocene precatalysts”and “metallocene catalyst precursor”, as used herein, shall beunderstood to refer to compounds possessing a transition metal M, withcyclopentadienyl (Cp) ligands, at least one non-cyclopentadienyl-derivedligand X, and zero or one heteroatom-containing ligand Y, the ligandsbeing coordinated to M and corresponding in number to the valencethereof. The metallocene catalyst precursors are generally neutralcomplexes but when activated with a suitable co-catalyst yield an activemetallocene catalyst which refers generally to an organometallic complexwith a vacant coordination site that can coordinate, insert, andpolymerize olefins. The metallocene catalyst precursor is preferably oneof, or a mixture of metallocene compounds of either or both of thefollowing types: (1) Cp complexes which have two Cp ring systems forligands (also referred to as a bis-Cp or bis-Cp complex); and (2)Monocyclopentadienyl complexes which have only one Cp ring system as aligand (also referred to as a mono-Cp or mono-Cp complex).

Cp complexes of the first type, i.e., group 1, have two Cp ring systemsfor ligands that form a sandwich complex with the metal and can be freeto rotate (unbridged) or locked into a rigid configuration through abridging group. The Cp ring ligands can be like or unlike,unsubstituted, substituted, or a derivative thereof such as aheterocyclic ring system which may be substituted, and the substitutionscan be fused to form other saturated or unsaturated rings systems suchas tetrahydroindenyl, indenyl, or fluorenyl ring systems. Thesecyclopentadienyl complexes have the general formula:(Cp ¹R¹ _(m))R³ _(n)(Cp ²R² _(p))MX_(q)wherein Cp¹ of ligand (Cp¹R¹ _(m)) and Cp² of ligand (Cp²R² _(p)) arethe same or different cyclopentadienyl rings R¹ and R² each is,independently, a halogen or a hydrocarbyl, halocarbyl,hydrocarbyl-substituted organometalloid or halocarbyl-substitutedorganometalloid group containing up to about 20 carbon atoms, m is 0 to5, p is 0 to 5, and two R₁ and/or R₂ substituents on adjacent carbonatoms of the cyclopentadienyl ring associated there with can be joinedtogether to form a ring containing from 4 to about 20 carbon atoms; R³is a bridging group, n is the number of atoms in the direct chainbetween the two ligands and is an integer from 0 to 8, preferably 0 to 3(where 0 indicates the absence of the bridging group); M is a transitionmetal having a valence of from 3 to 6, preferably from group 4, 5, or 6of the periodic table of the elements and is preferably in its highestoxidation state, each X is a non-cyclopentadienyl ligand and is,independently, a halogen or a hydride, or a hydrocarbyl, oxyhydrocarbyl,halocarbyl, hydrocarbyl-substituted organometalloid,oxyhydrocarbyl-substituted organometalloid or halocarbyl-substitutedorganometalloid group containing up to about 20 carbon atoms, q is equalto the valence of M minus 2.

The Cp ligand in monocyclopentadienyl complexes which have only one Cpring system, i.e., group 2, forms a half-sandwich complex with the metaland can be free to rotate (unbridged) or locked into a rigidconfiguration through a bridging group to a heteroatom-containingligand. The Cp ring ligand can be unsubstituted, substituted, or aderivative thereof such as a heterocyclic ring system which may besubstituted, and the substitutions can be fused to form other saturatedor unsaturated rings systems such as tetrahydroindenyl, indenyl, orfluorenyl ring systems. The heteroatom containing ligand is bound toboth the metal and optionally to the Cp ligand through the bridginggroup. The heteroatom itself is an atom with a coordination number ofthree from group VA, or a coordination number of two, from group VIA ofthe periodic table of the elements. These mono-cyclopentadienylcomplexes have the general formula:(Cp ¹R¹ _(m))R³ _(n)(YR² _(r))MX_(s)wherein R¹ is, each independently, a halogen or a hydrocarbyl,halocarbyl, hydrocarbyl-substituted organometalloid orhalocarbyl-substituted organometalloid group containing up to about 20carbon atoms, “m” is 0 to 5, and two R₁ substituents on adjacent carbonatoms of the cyclopentadienyl ring associated there with can be joinedtogether to form a ring containing from 4 to about 20 carbon atoms; R³is a bridging group, “n” is an integer from 0 to 3 (where 0 indicatesthe absence of the bridging group), M is a transition metal having avalence of from 3 to 6, preferably from group 4, 5, or 6 of the periodictable of the elements and is preferably in its highest oxidation state;Y is a heteroatom containing group in which the heteroatom is an elementwith a coordination number of three from Group VA or a coordinationnumber of two from group VIA preferably nitrogen, phosphorous, oxygen,or sulfur, r is 1 when Y has a coordination number of three and n is not0 or when Y has a coordination number of two and n is 0, r is 2 when Yhas a coordination number of three and n is 0, or r is 0 (meaning R² isabsent) when Y has a coordination number of two and n is not 0, R² is aradical selected from a group consisting of C₁ to C₂₀ hydrocarbylradicals, substituted C₁ to C₂₀ hydrocarbyl radicals, wherein one ormore hydrogen atoms is replaced with a halogen atom; and each X is anon-cyclopentadienyl ligand and is, independently, a halogen, a hydride,or a hydrocarbyl, oxyhydrocarbyl, halocarbyl, hydrocarbyl-substitutedorganometalloid, oxyhydrocarbyl-substituted organometalloid orhalocarbyl-substituted organometalloid group containing up to about 20carbon atoms, “s” is equal to the valence of M minus 2. In a preferredembodiment, the catalyst utilized is adi(p-triethylsilylphenyl)methenyl[(cyclopentadienyl)(2,7-di-tert-butylfluoren-9-yl)]hafniumdimethyl.

Examples of suitable biscyclopentadienyl metallocenes of the typedescribed in group 1 above are disclosed in U.S. Pat. Nos. 5,324,800;5,198,401; 5,278,119; 5,387,568; 5,120,867; 5,017,714; 4,871,705;4,542,199; 4,752,597; 5,132,262; 5,391,629; 5,243,001; 5,278,264;5,296,434; and 5,304,614; each of which is incorporated by referenceherein in its entirety.

In one or more embodiments, copolymerization techniques utilize morethan one catalyst, i.e., two or more bis-Cp catalysts, or two or moremono-Cp catalysts, or one or more bis-Cp catalysts, with one or moremono-Cp catalysts.

Activators

The catalyst precursors employed in the present process can also beactivated with cocatalysts or activators that comprise non-coordinatinganions or they can be activated with Lewis acid activators, or acombination thereof.

Ionic activators comprise non-coordinating anions. The term“non-coordinating anion” (NCA) means an anion which either does notcoordinate to said transition metal cation or which is only weaklycoordinated to said cation, thereby remaining sufficiently labile to bedisplaced by a neutral Lewis base. “Compatible” NCAs are those which arenot degraded to neutrality when the initially formed complex decomposes.Further, the anion will not transfer an anionic substituent or fragmentto the cation so as to cause it to form a neutral four coordinatemetallocene compound and a neutral by-product from the anion.Non-coordinating anions useful for the purposes herein are those whichare compatible, stabilize the metallocene cation in the sense ofbalancing its ionic charge in a +1 state, and yet retain sufficientlability to permit displacement by an ethylenically or acetylenicallyunsaturated monomer during polymerization. Additionally, the anionsuseful for the purposes herein will be large or bulky in the sense ofsufficient molecular size to largely inhibit or prevent neutralizationof the metallocene cation by Lewis bases other than the polymerizablemonomers that may be present in the polymerization process. Typically,the anion will have a molecular size of greater than or equal to about 4angstroms. NCAs are preferred because of their ability to produce atarget molecular weight polymer at a higher temperature than tends to bethe case with other activation systems such as alumoxane.

Descriptions of ionic catalysts for coordination polymerization usingmetallocene cations activated by NCAs appear in EP-A-0 277 003; EP-A-0277 004; WO92/00333; and U.S. Pat. Nos. 5,198,401, and 5,278,119, eachof which are herein incorporated by reference in their entirety. Thesereferences teach a preferred method of preparation wherein metallocenes(bis-Cp and mono-Cp) are protonated by an anionic precursors such thatan alkyl/hydride group is abstracted from a transition metal to make itboth cationic and charge-balanced by the NCA. The use of ionizing ioniccompounds not containing an active proton but capable of producing boththe active metallocene cation and a NCA are also known. See, e.g.,EP-A-0 426 637, EP-A-0 573 403, and U.S. Pat. No. 5,387,568, each ofwhich are herein incorporated by reference in their entirety. Reactivecations other than Bronsted acids capable of ionizing the metallocenecompounds include ferrocenium triphenylcarbonium and triethylsilyliniumcations.

Any metal or metalloid capable of forming a coordination complex whichis resistant to degradation by water (or other Bronsted or Lewis Acids)may be used or contained in the anion of the second activator compound.Suitable metals include, but are not limited to, aluminum, gold,platinum, and the like. Suitable metalloids include, but are not limitedto, boron, phosphorus, silicon, and the like. The description of NCAsand precursors thereto of these documents are incorporated herein byreference in their entirety.

An additional method of making the ionic catalysts uses ionizing anionicpre-cursors (Lewis acid activators) which are initially neutral Lewisacids but form the cation and anion upon ionizing reaction with themetallocene compounds, for example tris(pentafluorophenyl) boron acts toabstract an alkyl, hydride, or silyl ligand to yield a metallocenecation and stabilizing NCA, see, e.g., EP-A-0 427 697 and EP-A-0 520732, each of which are herein incorporated by reference in theirentirety. Ionic catalysts for addition polymerization can also beprepared by oxidation of the metal centers of transition metal compoundsby anionic precursors containing metallic oxidizing groups along withthe anion groups, see EP-A-0 495 375, which is herein incorporated byreference in its entirety.

Where the metal ligands include halide moieties, for example,(methyl-phenyl) silylene (tetramethylcyclopentadienyl)(tert-buty-amido)zirconium dichloride), which are not capable of ionizing abstractionunder standard conditions, they can be converted via known alkylationreactions with organometallic compounds such as lithium, or aluminumhydrides, or alkyls, alkylalumoxanes, Grignard reagents, etc. Processesdescribing the reaction of alkyl aluminum compounds with dihalidesubstituted metallocene compounds prior to or with the addition ofactivating anionic compounds are found in EP-A-0 500 944, EP-A1-0 570982, and EP-A1-0 612 768, each of which are herein incorporated byreference in their entirety. For example, an aluminum alkyl compound maybe mixed with the metallocene prior to its introduction into thereaction vessel. Since the alkyl aluminum is also suitable as ascavenger, its use in excess of that normally stoichiometricallyrequired for alkylation of the metallocene will permit its addition tothe reaction solvent with the metallocene compound. Normally alumoxanewould not be added with the metallocene so as to avoid prematureactivation, but can be added directly to the reaction vessel in thepresence of the polymerizable monomers when serving as both scavengerand alkylating activator. Alumoxanes may also fulfill a scavengingfunction.

Similarly, a co-activator is a compound capable of alkylating thetransition metal complex, such that when used in combination with anactivator, an active catalyst is formed. Co-activators includealumoxanes such as methyl alumoxane, modified alumoxanes such asmodified methyl alumoxane, and aluminum alkyls such trimethyl aluminum,tri-isobutyl aluminum, triethyl aluminum, and tri-isopropyl aluminum.Co-activators are typically used in combination with Lewis acidactivators and Ionic activators when the pre-catalyst is not adihydrocarbyl or dihydride complex.

Known alkylalumoxanes are additionally suitable as catalyst activators,particularly for those metallocenes comprising halide ligands. Thealumoxane component useful as catalyst activator typically is anoligomeric aluminum compound represented by the general formula(R—Al—O)_(n), which is a cyclic compound, or R(R—Al—O)₁AlR₂, which is alinear compound. In the general alumoxane formula R is a C₁ to C₅ alkylradical, for example, methyl, ethyl, propyl, butyl or pentyl and “n” isan integer from 1 to about 50. Most preferably, R is methyl and “n” isat least 4, i.e., methylalumoxane (MAO). Alumoxanes can be prepared byvarious procedures known in the art. For example, an aluminum alkyl maybe treated with water dissolved in an inert organic solvent, or it maybe contacted with a hydrated salt, such as hydrated copper sulfatesuspended in an inert organic solvent, to yield an alumoxane. Generally,however prepared, the reaction of an aluminum alkyl with a limitedamount of water yields a mixture of the linear and cyclic species of thealumoxane.

Polymerization Process

The ethylene-based copolymer is preferably polymerized in a single wellstirred tank reactor in solution where the viscosity of the solutionduring polymerization is less than 10000 cps, or less than 7000 cps, andpreferably less than 500 cps.

The reactor is preferably liquid filled, continuous flow, stirred tankreactors providing full back mixing for random copolymer production.Solvent, monomers, and catalyst are fed to the reactor. When two or morereactors are utilized, solvent, monomers, and/or catalyst is fed to thefirst reactor or to one or more additional reactors.

Reactors may be cooled by reactor jackets or cooling coils,autorefrigeration, prechilled feeds, or combinations of all three toabsorb the heat of the exothermic polymerization reaction.Autorefrigerated reactor cooling requires the presence of a vapor phasein the reactor. Adiabatic reactors with prechilled feeds are preferred,in which the polymerization exotherm is absorbed by permitting atemperature rise of the polymerizing liquid.

Use of hydrogen to control molecular weight may be avoided or reduced,if desired. The reactor temperature may be used to control the molecularweight of the polymer fraction produced. In series operation, this givesrise to a temperature difference between reactors which is helpful forcontrolling polymer molecular weight. In one or more embodiments, thistechnique is used to prepare bimodal copolymers.

Reactor temperature is selected, depending upon the effect oftemperature on catalyst deactivation rate, and polymer properties,and/or extent of monomer depletion. For best monomer conversion, it isdesirable to operate at as high a temperature as possible usingrelatively concentrated polymer solutions.

When using more than one reactor, generally temperatures should notexceed the point at which the concentration of catalyst in the secondreactor is insufficient to make the desired polymer component in thedesired amount.

Therefore, reaction temperature is determined by the details of thecatalyst system. In general, a single reactor or first reactor in aseries will operate at a reactor temperature from about 0° C. to about120° C., or from about 0° C. to about 110° C., or from about 40° C. toabout 100° C. Preferably, reaction temperatures are from about 10° C. toabout 90° C., or more preferably from about 20° C. to about 70° C., orfrom about 80° C. to about 120° C. When using on or more additionalreactors, the additional reactor temperature will vary from 40-160° C.,with 50-140° C. preferred, and 60-120° C. more preferred. Ranges fromany of the recited lower limits to any of the recited upper limits arecontemplated by the inventors and within the scope of the presentdescription.

In copolymerization techniques that utilize both a one or more bis-Cpcatalysts with one or more mono-Cp catalysts, a lower reactiontemperature is preferred for reactions utilizing mono-Cp catalyst whencompared to the bis-Cp catalyst.

Reaction pressure is determined by the details of the catalyst system.In general reactors, whether a single reactor or each of a series ofreactors, operates at a reactor pressure of less than 600 pounds persquare inch (psi) (4.134 Mpa), or less than 500 psi (3.445 Mpa), or lessthan 400 psi (2.756 Mpa), or less than 300 psi (2.067 Mpa). Preferably,reactor pressure is from about atmospheric pressure to about 400 psi(2.756 Mpa), or from about 200 psi (1.378 Mpa) to about 350 psi (2.411Mpa), or from about 300 psi (2.067 Mpa) to about 375 psi (2.584 Mpa).Ranges from any of the recited lower limits to any of the recited upperlimits are contemplated by the inventors and within the scope of thepresent description.

In the case of less stable catalysts, catalyst can also be fed to asecond reactor when the selected process uses reactors in series.Optimal temperatures can be achieved, particularly for series operationwith progressively increasing polymerization temperature, by usingbis-Cp catalyst systems containing hafnium as the transition metal,especially those having a covalent, single atom bridge coupling the twocyclopentadienyl rings.

Particular reactor configurations and processes suitable for use in theprocesses described herein are described in detail in U.S. patentapplication Ser. Nos. 09/260,787, filed Mar. 1, 1999, and 60/243,192,filed Oct. 25, 2000, the disclosures of which are incorporated herein byreference in their entireties.

Preferably, the linearity of the ethylene-based copolymers is preservedduring polymerization. Branching is introduced by the choice ofpolymerization catalysts, process condition as the choice of thetransfer agent. High polymerization temperatures lead to branchedpolymers as does the use of thermally induced transfer.

The copolymerization process may occur with or without hydrogen present.However, hydrogen is a preferred chain transfer agent because itinhibits branching in the copolymers since it lead to chain ends whichare completely or substantially saturated. Without being limited bytheory, it is believed that these saturated polymers cannot participatein the principal branching pathway where preformed polymers withunsaturated chain ends are reincorporated into new growing chains whichlead to branched polymers. Lower polymerization temperatures also leadto lower branching since the formation of chains with unsaturated endsis inhibited by lower scission processes.

Lubricating Oil Compositions

Lubricating oil composition are composed of at least one ethylene-basedpolymer and at least one lubrication oil base. Thus, ethylene-basedpolymers are used as viscosity modifiers for lubrication fluids. In someembodiments, lubricating oil compositions are composed of: (a) two ormore ethylene-based copolymers and a lubricating oil base; (b) anethylene-based copolymer and two or more lubricating oil bases; or (c)two or more ethylene-based copolymers and two or more lubricating oilbases. In one or more embodiments, the lubricating oil compositionsinclude one or more conventional additives that are known to thoseskilled in the art. A preferred additive is a pour point depressant.

As used herein Viscosity Index (VI) is the ability of a lubricating oilto accommodate increases in temperature with a minimum decrease inviscosity. The greater this ability, the higher the VI.

Relative performance of VI improving compositions may be measured by TEand/or ratio of TE/SSI. TE and SSI reflect the efficacy of the increasein viscosity and the persistence of the increased viscosity underconditions of high shear, respectively. TE is measured in a dilute orsemidilute solution in base oil according to ASTM D445. Shear stabilityindex is measured in a dilute or semidilute solution in base oilaccording to ASTM D6278. In this usage, relative performance increases,or is considered more desirable, as TE increases and SSI valuesdecrease.

In the industry the generally accepted procedure is to use theappropriate amount of the olefin copolymer viscosity improver to raisethe viscosity of the basestock oil by a predetermined amount. At higherTE effectively less of the rheology modifier is needed to have a similarincrease in the viscosity of the base stock oil. This diminished useleads to a substantially simpler formulation where other additives suchas pour point depressants can be decreased or eliminated compared toequivalent formulation made with conventional viscosity modifiers.

It is generally believed that the composition of the olefin copolymerand the average molecular weight largely determine the TE which isfavored by increases in either area. Thus, higher ethylene contentrheology modifiers are preferred because of their higher TE. Whileincreasing ethylene content leads to improved TE/SSI ratios, thecompositional change also leads to increasing crystallinity of theolefin copolymer. Crystallinities are apparent as measured by DSC atcompositions near or above 45 wt. % ethylene for ethylene propylenecopolymers. This detracts from the performance as a VI improver sincethese crystalline polymers tend to flocculate, either by themselves orin association with other components of the lubricating oil andprecipitate out of the lubricating oils. These precipitates are apparentas regions (‘lumps’) of high viscosity or essentially completesolidification (gels) and can lead to clogs and blockages of pumps andother passageways for the lubrication fluid and can lead to harm and insome cases failure of moving machinery.

An alternate mode of raising the TE of a rheology modifying compositionsis to raise the molecular weight. This method is effective, but alsoleads to higher, and therefore detrimental, SSI characteristics. Thus, ahigher molecular weight polymer, while effective in raising theviscosity of the basestock oil, also leads to a temporary effect sincethe increase in viscosity rapidly disappears in a region of high shearas the molecular weight of the polymer rapidly degrades. It is easy tounderstand that in a polymer sample containing a distribution ofmolecular weights the most rapid degradation of molecular weights in ahigh shear region would be for the molecules with the highest molecularweights, since these molecules with the longest backbone length would bemost susceptible to a random chain scission mechanism.

While not being bound by any particular theory, it is believed thatlubrication fluids composed of the present ethylene-based copolymer,have near the most probable distribution of molecular weight, i.e.,having a PDI less than about 2.4, preferably less than about 2.3, andmore preferably less than about 2.2 as measured by GPC, and are bothintra and inter molecularly uniform. Such lubricating oil compositionswill have a higher TE and be less prone to the deleterious effects ofmacroscopic crystallization in dilute solution as measured by the changein the rheology of the fluid solution compared to an equivalent amountof an ethylene copolymer which does not have these structurallimitations. This effect will be most noted in solution at subambient,ambient, and supra ambient temperatures.

It is also believed that these ethylene-based copolymer will have lowercrystallinization on cooling from ambient to sub-ambient temperatures,resulting in better low temperature flow properties in solution, ascompared to equivalent compositionally uniform polymers of similarmolecular weight and TE. Dilute solutions of ethylene-based copolymersdisplay a higher TE and lower SSI compared to similar conventionalcompositions. The present ethylene-based copolymers have a superior lowtemperature performance as measured by reduced viscosity of thesolutions at low temperature.

Generally, the TE of a polyolefin copolymer is a function of thecomposition. For ethylene-based copolymers, in particular thosecontaining propylene comonomers, TE increases with ethylene content ofthe polymer. FIG. 1 illustrates the effect of ethylene content where theTE of various ethylene-propylene copolymers of different compositions isplotted.

The ethylene-based copolymers described herein have an unusually high TEwith respect to the known and conventional viscosity improvingcompositions for similar SSI. While not wishing to be bound byspeculation, it is believed that this unexpected and beneficialattribute of the polymer arises from a predetermined control ofmolecular structure which comprises all or some of the following parts:

-   -   1. The ethylene-based copolymer molecule is rigorously narrow in        composition both intramolecularly, and intermolecularly.    -   2. The ethylene-based copolymer is the “most probable” molecular        weight distribution without substantial molecular weight        digression, in either the high or the low molecular weight end        of the distribution.    -   3. The ethylene-based copolymer molecule is linear with little        or negligible evidence of long chain branching, as determined by        rheological and molecular weight measurements.

As shown in FIG. 1, such ethylene-based copolymers have a TE that isreproducibly higher than that of other competitive polymers with similarethylene concentration. When combinations of characteristics 1-3 arepresent, or all are present, the resultant ethylene-based copolymers arehighly effective and yet do not have low temperature viscometricsproblems characteristic of high TE viscosity modifiers. For example, theTE of an ethylene-based polymer with a 48 wt. % ethylene content iscomparable to existing polymers, such as Paratone 8900K, which has anethylene content 64 wt. %.

In some embodiments of lubricant oil compositions, the ethylene-basedcopolymer has an ethylene content of less than about 80 wt. %, or morepreferably less than 78 wt. %, and even more preferably less than 76 wt.%, and even more preferably less than 74 wt. %. It is also desirablethat the ethylene content of the ethylene-based copolymer be greaterthan 25 wt. % ethylene, or greater than 30 wt. % ethylene, or greaterthan 35 wt. % ethylene, and greater than 40 wt. % ethylene.

In some embodiments of lubricant oil compositions, the ethylene-basedcopolymer has a molecular weight measured as the number averagemolecular weight by GPC of more than about 20,000, or more than about25,000, or preferably more than about 30,000. The molecular weightmeasured as the number average molecular weight by GPC is less thanabout 200,000, or less than about 180,000, or less than about 150,000,and preferably less than about 120,000.

In some embodiments of lubricant oil compositions, the ethylene-basedcopolymer has a molecular weight distribution as close to “mostprobable” distribution, but less than 2.4 PDI, or less than 2.3 PDI, orless than 2.2 PDI.

In some embodiments of lubricant oil compositions, the ethylene-basedcopolymer is compositionally homogeneous both intermolecularly andintramolecularly with less than about 15 wt. %, or preferably less thanabout 10 wt. %, and preferably less than about 5 wt. % of the polymersegments having a composition greater than 1 standard deviation awayfrom the mean composition.

In some embodiments of lubricant oil compositions, the ethylene-basedcopolymer is linear with less than 1 branch point along 200 carbon atomsalong a backbone, or less than 1 per 300 branchpoints, or less than 1per 500 carbon atoms, and preferably less than 1 per 1000 carbon atomsnotwithstanding the presence of branch points due to incorporation ofthe comonomer.

Lubricating Oil Base

As used herein, lubricating oil bases include each conventionallubricating oil bases known to those skilled in the art. Examples of thelubricating oil bases include mineral oils and synthetic oils such aspoly-α-olefins, polyol esters, and polyalkylene glycols. A mineral oilor a blend of a mineral oil and a synthetic oil is preferably employed.The mineral oil is generally used after subjected to purification suchas dewaxing. Although mineral oils are divided into several classesaccording to the purification method, generally used is a mineral oilhaving a wax content of about 0.5 to about 10 wt. %. Further, a mineraloil having a kinematic viscosity of 10 to 200 cSt is generally used.

Suitable base oils include those conventionally employed as crankcaselubricating oils for spark-ignited and compression-ignited internalcombustion engines, such as automobile and truck engines, marine andrailroad diesel engines, and the like. Advantageous results are alsoachieved by employing the ethylene-based copolymers in base oilsconventionally employed in and/or adapted for use as power transmittingfluids such as automatic transmission fluids, tractor fluids, universaltractor fluids and hydraulic fluids, heavy duty hydraulic fluids, powersteering fluids and the like. Gear lubricants, industrial oils, pumpoils and other lubricating oil compositions can also benefit from theincorporation of the present ethylene-based copolymers.

Suitable base oils include not only hydrocarbon oils derived frompetroleum, but also include synthetic lubricating oils such as esters ofdibasic acids, complex esters made by esterification of monobasic acids,polyglycols, dibasic acids and alcohols, polyolefin oils, etc. Thus,ethylene-based copolymers are suitably incorporated into synthetic baseoils such as alkyl esters of dicarboxylic acids, polyglycols andalcohols, polyalpha-olefins, polybutenes, alkyl benzenes, organic estersof phosphoric acids, polysilicone oils.

The above oil compositions may optionally contain other conventionaladditives, such as, for example, pour point depressants, antiwearagents, antioxidants, other viscosity-index improvers, dispersants,corrosion inhibitors, anti-foaming agents, detergents, rust inhibitors,friction modifiers, and the like.

Corrosion inhibitors, also known as anti-corrosive agents, reduce thedegradation of the metallic parts contacted by the lubricating oilcomposition. Illustrative of corrosion inhibitors are phosphosulfurizedhydrocarbons and the products obtained by reaction of aphosphosulfurized hydrocarbon with an alkaline earth metal oxide orhydroxide, preferably in the presence of an alkylated phenol or of analkylphenol thioester, and also preferably in the presence of carbondioxide. Phosphosulfurized hydrocarbons are taught in U.S. Pat. No.1,969,324, the disclosure of which is incorporated herein by reference.

Oxidation inhibitors, or antioxidants, reduce the tendency of mineraloils to deteriorate in service, as evidenced by the products ofoxidation such as sludge and varnish-like deposits on the metalsurfaces, and by viscosity growth. Such oxidation inhibitors includealkaline earth metal salts of alkylphenolthioesters having C₅ to C₁₂alkyl side chains, e.g., calcium nonylphenate sulfide, bariumoctylphenate sulfide, dioctylphenylamine, phenylalphanaphthylamine,phosphosulfurized or sulfurized hydrocarbons, etc.

Other oxidation inhibitors or antioxidants useful in this inventioninclude oil-soluble copper compounds, such as described in U.S. Pat. No.5,068,047, the disclosure of which is incorporated herein by reference.

Friction modifiers serve to impart the proper friction characteristicsto lubricating oil compositions such as automatic transmission fluids.Representative examples of suitable friction modifiers are found in:U.S. Pat. No. 3,933,659, which discloses fatty acid esters and amides;U.S. Pat. No. 4,176,074, which describes molybdenum complexes ofpolyisobutenyl succinic anhydride-amino alkanols; U.S. Pat. No.4,105,571, which discloses glycerol esters of dimerized fatty acids;U.S. Pat. No. 3,779,928, which discloses alkane phosphonic acid salts;U.S. Pat. No. 3,778,375, which discloses reaction products of aphosphonate with an oleamide; U.S. Pat. No. 3,852,205, which disclosesS-carboxyalkylene hydrocarbyl succinimide, S-carboxyalkylene hydrocarbylsuccinamic acid and mixtures thereof; U.S. Pat. No. 3,879,306, whichdiscloses N(hydroxyalkyl)alkenyl-succinamic acids or succinimides; U.S.Pat. No. 3,932,290, which discloses reaction products of di-(loweralkyl) phosphites and epoxides; and U.S. Pat. No. 4,028,258 whichdiscloses the alkylene oxide adduct of phosphosulfurizedN-(hydroxyalkyl)alkenyl succinimides. Preferred friction modifiers aresuccinate esters, or metal salts thereof, of hydrocarbyl substitutedsuccinic acids, or anhydrides and thiobis-alkanols, such as described inU.S. Pat. No. 4,344,853. The disclosures of the patents identified inthis paragraph are each incorporated by reference herein in theirentirety.

Dispersants maintain oil insolubles, resulting from oxidation duringuse, in suspension in the fluid, thus preventing sludge flocculation andprecipitation or deposition on metal parts. Suitable dispersants includehigh molecular weight N-substituted alkenyl succinimides, the reactionproduct of oil-soluble polyisobutylene succinic anhydride with ethyleneamines such as tetraethylene pentamine and borated salts thereof. Highmolecular weight esters (resulting from the esterification of olefinsubstituted succinic acids with mono or polyhydric aliphatic alcohols)or Mannich bases from high molecular weight alkylated phenols (resultingfrom the condensation of a high molecular weight alkylsubstitutedphenol, an alkylene polyamine and an aldehyde such as formaldehyde) arealso useful as dispersants.

Pour point depressants, otherwise known as lube oil flow improvers,lower the temperature at which the fluid will flow or can be poured.Such additives are well known in the art. Typically of those additiveswhich usefully optimize the low temperature fluidity of the fluid are C₈to C₁₈ dialkylfumarate vinyl acetate copolymers, polymethacrylates, andwax naphthalene.

Foam control can be provided by an antifoamant of the polysiloxane type,e.g., silicone oil and polydimethyl siloxane.

Anti-wear agents, as their name implies, reduce wear of metal parts.Representatives of conventional antiwear agents are zincdialkyldithiophosphate and zinc diaryldithiosphate, which also serves asan antioxidant.

Detergents and metal rust inhibitors include the metal salts ofsulphonic acids, alkyl phenols, sulfurized alkyl phenols, alkylsalicylates, naphthenates and other oil soluble mono- and dicarboxylicacids. Highly basic (viz, overbased) metal sales, such as highly basicalkaline earth metal sulfonates (especially Ca and Mg salts) arefrequently used as detergents.

Lubricating oil compositions include an effective amount ofethylene-based copolymer to improve or modify the VI of the base oil,i.e., a viscosity improving effective amount. Generally, this amount isfrom about 0.001 to about 20 wt. %, based on the weight of thelubricating oil composition, for a finished product (e.g., a fullyformulated lubricating oil composition), with alternative lower limitsof 0.01 wt. %, 0.1 wt. %, or 1 wt. %, and alternative upper limits ofabout 15 wt. % or about 10 wt. %, in other embodiments.

Preferably, the ethylene-based copolymer, or grafted and/or derivatizedversion thereof, has a solubility in oil of at least about 10 wt. %. Inone or more embodiments, from about 0.001 to 49 wt. % of thiscomposition is incorporated into a base oil, such as a lubricating oilor a hydrocarbon fuel, depending upon whether the desired product is afinished product or an additive concentrate. Ranges from any of therecited lower limits to any of the recited upper limits are within thescope of the present description.

In one or more embodiments, where lubricating oil compositions arecomposed of additives, additives are typically blended into the base oilin amounts which are effective to provide their normal attendantfunction. Thus, typical formulations can include, in amounts by weight,one or more ethylene-based copolymers (0.01-12%); a corrosion inhibitor(0.01-5%); an oxidation inhibitor (0.01-5%); depressant (0.01-5%); ananti-foaming agent (0.001-3%); an anti-wear agent (0.001-5%); a frictionmodifier (0.01-5%); a detergent/rust inhibitor (0.01-10%); and an oilbase.

When other additives are used, it may be desirable, although notnecessary, to prepare additive concentrates comprising concentratedsolutions or dispersions of the ethylene-based copolymers together withone or more of the other additives, such a concentrate denoted an“additive package,” whereby several additives can be addedsimultaneously to the base oil to form a lubricating oil composition.

Dissolution of the additive concentrate into the lubricating oil may befacilitated by solvents and by mixing accompanied with mild heating, butthis is not essential. The additive-package will typically be formulatedto contain an ethylene-based copolymer and optional additional additivesin proper amounts to provide the desired concentration in the finalformulation when the additive-package is combined with a predeterminedamount of base lubricant. Thus, rheology modifying compositions can beadded to small amounts of base oil or other compatible solvents alongwith other desirable additives to form additive-packages containingactive ingredients in collective amounts of typically from about 2.5 toabout 90 wt. %, preferably from about 5 to about 75 wt. %, and stillmore preferably from about 8 to about 50 wt. % by weight additives inthe appropriate proportions with the remainder being base oil. In one ormore embodiments, the final lubricating oil composition may use about 10wt. % of the additive-package with the remainder being base oil.

In one or more embodiments, the rheology modifying compositions areutilized in a concentrate form, such as from 1 wt. % to 49 wt. % in oil,e.g., mineral lubricating oil, for ease of handling, and may be preparedin this form by carrying out the reaction of the invention in oil aspreviously described.

Methods of Preparing Lubricating Oil Compositions

Rheology modifying compositions are blended with base oils to formlubricant oil compositions. Conventional blending methods are describedin U.S. Pat. No. 4,464,493, the disclosure of which is incorporatedherein by reference. This conventional process requires passing thepolymer through an extruder at elevated temperature for degradation ofthe polymer and circulating hot oil across the die face of the extruderwhile reducing the degraded polymer to particle size upon issuance fromthe extruder and into the hot oil. The pelletized, solid rheologymodifying compositions are added by blending directly with the base oil,so that the conventional complex multi-step processes of the prior artare not needed. The solid polymer composition can be dissolved in thebase oil without the need for additional shearing and degradationprocesses.

In embodiments where a viscosity modifying concentrate is prepared, theethylene-based copolymer will be soluble at room temperature in lubeoils at up to 10 percent concentration. Such concentrate, includingeventually an additional additive package including the typicaladditives used in lube oil application as described above, is generallyfurther diluted to the final concentration, typically about 1 wt. %, bymulti-grade lube oil producers. In this case, the concentrate will be apourable homogeneous solid free solution.

In one or more embodiments, ethylene-based copolymers have a SSI lessthan about 100, or less than about 80, or less than about 60, or lessthan about 50, or less than about 40. Preferably, ethylene-basedcopolymers have a SSI of from about 1 to about 60, or from about 10 toabout 60, or from about 20 to about 60 or from about 10 to about 50.Ranges from any of the recited lower limits to any of the recited upperlimits are within the scope of the present description.

Polymer Analysis

Unless stated otherwise, the following analysis techniques were utilizedto characterize the various compositions and components describedherein. Unless stated otherwise, the following analysis techniques applyto all characterization properties described above.

Ethylene wt. % was determined according to ASTM D1903.

DSC Measurements

The crystallization temperature Tc and melting temperature Tm ofpolymers, e.g., ethylene-based copolymers, were measured using a TAInstruments Model 2910 DSC. Typically, 6-10 mg of a polymer was sealedin a pan with a hermetic lid and loaded into the instrument. In anitrogen environment, the sample was first cooled to −100° C. at 20°C./min. It was heated to 220° C. at 10° C./min and melting data (firstheat) were acquired. This provides information on the melting behaviorunder as-received conditions, which can be influenced by thermal historyas well as sample preparation method. The sample was then equilibratedat 220° C. to erase its thermal history. Crystallization data (firstcool) were acquired by cooling the sample from the melt to −100° C. at10° C./min and equilibrated at −100° C. Finally, it was heated again to220° C. at 10° C./min to acquire additional melting data (second heat).The endothermic melting transition (first and second heat) andexothermic crystallization transition (first cool) were analyzed forpeak temperature and area under the peak. The term “melting point,” asused herein, is the highest peak among principal and secondary meltingpeaks as determined by DSC during the second melt, discussed above. Thethermal output is recorded as the area under the melting peak of thesample, which is typically at a maximum peak at about 30° C. to about175° C., and occurs between the temperatures of about 0° C. and about200° C. The thermal output is measured in Joules as a measure of theheat of fusion. The melting point is recorded as the temperature of thegreatest heat absorption within the range of melting of the sample.

Size-Exclusion Chromatography of Polymers (SEC-3D)

Molecular weight (weight-average molecular weight, M_(w), number-averagemolecular weight, M_(n), and molecular weight distribution, M_(w)/M_(n)or MWD) were determined using a High Temperature Size ExclusionChromatograph (either from Waters Corporation or Polymer Laboratories),equipped with a differential refractive index detector (DRI), an onlinelight scattering (LS) detector, and a viscometer. Experimental detailsnot described below, including how the detectors were calibrated, aredescribed in T. Sun et al., Macromolecules, 34 (19), pp. 6812-6820,(2001).

Three Polymer Laboratories PLgel 10 mm Mixed-B columns were used. Thenominal flow rate was 0.5 cm³/min, and the nominal injection volume was300 μL. The various transfer lines, columns and differentialrefractometer (the DRI detector) were contained in an oven maintained at145° C. Solvent for the SEC experiment was prepared by dissolving 6grams of butylated hydroxy toluene as an antioxidant in 4 liters ofAldrich reagent grade 1, 2, 4 trichlorobenzene (TCB). The TCB mixturewas then filtered through a 0.7 μm glass pre-filter and subsequentlythrough a 0.1 μm Teflon filter. The TCB was then degassed with an onlinedegasser before entering the SEC. Polymer solutions were prepared byplacing dry polymer in a glass container, adding the desired amount ofTCB, then heating the mixture at 160° C. with continuous agitation forabout 2 hours. All quantities were measured gravimetrically. The TCBdensities used to express the polymer concentration in mass/volume unitsare 1.463 g/ml at room temperature and 1.324 g/ml at 145° C. Theinjection concentration ranged from 1.0 to 2.0 mg/ml, with lowerconcentrations being used for higher molecular weight samples. Prior torunning each sample the DRI detector and the injector were purged. Flowrate in the apparatus was then increased to 0.5 ml/minute, and the DRIwas allowed to stabilize for 8-9 hours before injecting the firstsample. The LS laser was turned on 1 to 1.5 hours before runningsamples.

The concentration, c, at each point in the chromatogram is calculatedfrom the baseline-subtracted DRI signal, I_(DRI), using the followingequation:c=K _(DRI) I _(DRI)/(dn/dc)where K_(DRI) is a constant determined by calibrating the DRI, and(dn/dc) is the same as described below for the light scattering (LS)analysis. Units on parameters throughout this description of the SECmethod are such that concentration is expressed in g/cm³, molecularweight is expressed in g/mole, and intrinsic viscosity is expressed indL/g.

The light scattering detector used was a Wyatt Technology HighTemperature mini-DAWN. The polymer molecular weight, M, at each point inthe chromatogram is determined by analyzing the LS output using the Zimmmodel for static light scattering (M. B. Huglin, LIGHT SCATTERING FROMPOLYMER SOLUTIONS, Academic Press, 1971):

$\frac{K_{o}c}{\Delta\;{R(\theta)}} = {\frac{1}{{MP}(\theta)} + {2\; A_{2}c}}$Here, ΔR(θ) is the measured excess Rayleigh scattering intensity atscattering angle θ, c is the polymer concentration determined from theDRI analysis, A₂ is the second virial coefficient [for purposes of thisinvention and the claims thereto, A₂=0.0006 for propylene polymers and0.001 otherwise], P(θ) is the form factor for a monodisperse random coil(M. B. Huglin, LIGHT SCATTERING FROM POLYMER SOLUTIONS, Academic Press,1971), and K_(o) is the optical constant for the system:

$K_{o} = \frac{4\pi^{2}{n^{2}\left( {{\mathbb{d}n}/{\mathbb{d}c}} \right)}^{2}}{\lambda^{4}N_{A}}$in which N_(A) is Avogadro's number, and (dn/dc) is the refractive indexincrement for the system. The refractive index, n=1.500 for TCB at 145°C. and λ=690 nm. For purposes of this invention and the claims thereto(dn/dc)=0.104 for propylene polymers and 0.1 otherwise.

A high temperature Viscotek Corporation viscometer, which has fourcapillaries arranged in a Wheatstone bridge configuration with twopressure transducers, was used to determine specific viscosity. Onetransducer measures the total pressure drop across the detector, and theother, positioned between the two sides of the bridge, measures adifferential pressure. The specific viscosity, η_(s), for the solutionflowing through the viscometer is calculated from their outputs. Theintrinsic viscosity, [η], at each point in the chromatogram iscalculated from the following equation:η_(s) =c[η]+0.3(c[η])²where c is concentration and was determined from the DRI output.

The branching index (g′) is calculated using the output of theSEC-DRI-LS-VIS method as follows. The average intrinsic viscosity,[η]_(avg), of the sample is calculated by:

$\lbrack\eta\rbrack_{avg} = \frac{\sum{c_{i}\lbrack\eta\rbrack}_{i}}{\sum c_{i}}$where the summations are over the chromatographic slices, i, between theintegration limits. The branching index g′ is defined as:

$g^{\prime} = \frac{\lbrack\eta\rbrack_{avg}}{{kM}_{v}^{\alpha}}$where, for purpose of this invention and claims thereto, α=0.695 forethylene, propylene, and butene polymers; and k=0.000579 for ethylenepolymers, k=0.000228 for propylene polymers, and k=0.000181 for butenepolymers. M_(v) is the viscosity-average molecular weight based onmolecular weights determined by LS analysis.Temperature Rising Elution Fractionation (TREF)

The determination of intermolecular compositional heterogeneity wasdetermined by the fractionation of the ethylene-based copolymer wascarried out by a Polymer Char TREF 200 based on a well-known principle:the solubility of a semi-crystalline copolymer is a strong function oftemperature. The heart of the instrument is a column packed with solidstainless-steel beads. The copolymer of interest was dissolved in 1,2ortho-dichlorobenzene (oDCB) at 160° C. for 60 min. Half of a milliliter(ml) of the polymer solution (concentration=4-5 mg/ml) was injected inthe column and it was stabilized there at 140° C. for 45 min. Thesolution was cooled from 140° C. to −15° C. at 1° C./min andequilibrated at this temperature for 10 min. This caused the copolymerto crystallize out of the quiescent solution in successive layers ofdecreasing crystallinity onto the surface of the beads. Pure solvent(oDCB) was pumped for 5 min at −15° C. at a flow rate of 1 ml/minthrough an infrared detector. A valve was then switched to allow thischilled oDCB to flow through the column at the same flow rate at −15° C.for 10 min. The material eluted was designated as the soluble fractionof the copolymer. At this point, the heater was on and the solventcontinued to flow through both the column and the infrared detectorwhile the temperature was programmed upward at a controlled rate of 2°C./min to 140° C. The infrared detector continuously measured theconcentration of the copolymer in the effluent from the column, and acontinuous solubility distribution curve was obtained.

Procedure for Gelation Visual Test

Place 10 ml sample of the solution into 40 ml glass vial with screw cap.A typical vial is available from VWR Corporation as catalog number (VWRcat #: C236-0040). Then heat the sample in an 80° C. oven for 1 hour toremove any thermal history. Store the vial at 10° C. for 4-6 hr in a LowTemperature Incubator. A typical incubator is available from VWRcorporation as catalog number 35960-057. Then store the vial at −15°C.+/−0.5° C. overnight in a chest freezer. A typical chest freezer isRevco Model UTL 750-3-A30. A thermocouple is placed into a referencevial, identical to the sample but containing only the solvent or baseoil to monitor the actual sample temperature. After 16 hours remove thevial from the freezer, do not remove the cap and immediately tilt thevial 80-90 degrees to an almost horizontal position. If condensationforms on the outside of the vial quickly wipe the vial with a papertowel. Use the following visual grading to rate the sample visually.

TABLE 1 GRADE DESCRIPTION DETAILED COMMENTS 0 No gel Free flowing fluidwith mirror surface 1 Light gel Slight non-homogeneity, surfaceroughness 2 Medium gel Large non-homogeneity, slight pulling away fromvial 3 Heavy gel Pulls away from vial, large visible lumps 4 Solid Solidgel

Anton-Parr Low Temperature Solution Rheology (low temperature rheology)experiments were done on an Anton-Parr Model MCR501 rheometer using a 1″cone and plate setup. The cone has a nominal 1 degree angle and 50micron gap. About 100 microliters of sample is deposited on the bottomplate using a syringe-pipette. The cone is then lowered onto the plateso that the volume between the cone and plate is fully occupied bysolution. The temperature is then lowered at a cooling rate of 1.5°C./min. while measuring the complex viscosity at an angular frequency of0.1 radians/sec., applying a 10% strain and recording a value everyminute. The viscosity at 0.1 rad/sec is then plotted as a function oftemperature to observe the effect of gelation. “Complex viscosity” asused herein means a frequency-dependent viscosity function determinedduring forced small amplitude harmonic oscillation of shear stress, inunits of Pascal-seconds, that is equal to the difference between thedynamic viscosity and the out-of-phase viscosity (imaginary part ofcomplex viscosity).

As used herein, any data generated using a Scanning BrookfieldViscometer Operation was gathered using procedures provided in ASTMD5133. Pour 25 to 30 ml of the sample into glass stator to the fill linewhich was immersed into an oil bath which is programmed to cool from −5°C. to −40° C. at 1° C./hour scanning speed. Pre-heat the sample to 90°C. for 90 minutes to remove thermal history. The temperature rampingprogram is set to cool from −5° C. to −40° C. at 1° C./hour scanningspeed. In sample collection mode, the Gelation Index (GI) and maximumviscosity can be viewed. The torque versus temperature data set can beconverted to a viscosity-temperature plot at which a gelation pointand/or corresponding gelation index can be established.

Melt Flow Rate of the polymers was measured according to ASTM D1238 at230° C., with a 2.16 kg load.

Kinematic viscosity was measured at 100° C. according to ASTM D445.

Thickening Efficiency (TE) was determined according to ASTM D445.

High temperature high shear (HTHS) viscosity was measured at 150° C.according to ASTM D5481.

Cold cranking simulator (CCS) tests were performed at −20° C. accordingto ASTM D5293.

Mini rotary viscometer (MRV) tests were performed at −30° C. accordingto ASTM D4684.

Pour point was determined according to ASTM D97.

Shear stability index (SSI) was determined according to ASTM D6278 at 30and 90 passes using a Kurt Ohban machine.

Shear stress data was determined by first heating the sample to −15° C.,and waiting for 15 minutes. Then while measuring the shear stress,applying a logarithmically increasing strain by varying the shear ratelogarithmically from 10⁻³ to 10 with 20 points/decade and 1 seconds perpoint.

The number of branch points was determined by measuring the radius ofgyration of polymers as a function of the molecular weight by themethods of size exclusion chromatography augmented by laser lightscattering. These procedures are described in the publications “A Studyof the Separation Principle in Size Exclusion Chromatography” by T Sunet al., Macromolecules, 2004, 37 (11), pp 4304-4312 and “Effect of ShortChain Branching on the Coil Dimensions of Polyolefins in DiluteSolution” by T Sun et al., Macromolecules, 2001, 34 (19), pp 6812-6820,which are both incorporated by reference.

Branching in ethylene-based copolymers can also be described by theratio of the TE to the MFR@230° C. measured at a load of 2.16 Kg. Highvalues of this parameter indicate low levels of branching while lowlevels indicate substantial levels of branching.

Further embodiments of ethylene-based copolymers and uses thereof areprovided in the following embodiments:

A. An ethylene-based copolymer comprising:

-   -   from about 35 wt. % to about 80 wt. % units derived from        ethylene, and    -   at least 1.0 wt. % or more of an α-olefin comonomer having 3 to        20 carbon atoms, based on the weight of the ethylene-based        copolymer,        wherein the ethylene-based copolymer has:    -   a melting peak (Tm), as measured by DSC, of 80° C. or less;    -   a polydispersity index of about 2.8 or less; and    -   has an intramolecular composition distribution of about 15 wt. %        or less.        B. The ethylene-based copolymer of embodiment A, wherein the        ethylene-based copolymer composition comprises from about 35 wt.        % to about 60 wt. % units derived from ethylene, based on the        weight of the ethylene-based copolymer.        C. The ethylene-based copolymer of embodiment A or B, wherein        the ethylene-based copolymer is substantially linear.        D. The ethylene-based copolymer of any of embodiments A-C,        wherein the α-olefin comonomer is derived from propylene,        butene, hexene, or octene.        E. The ethylene-based copolymer of any of embodiments A-D,        wherein the ethylene-based copolymer is an ethylene/propylene        copolymer.        F. The ethylene-based copolymer of any of embodiments A-E,        wherein the ethylene-based copolymer is a metallocene catalyzed        copolymer.        G. The ethylene-based copolymer of any of embodiments A-F,        wherein the ethylene-based copolymer has a weight-average        molecular weight (Mw) of from about 80,000 to about 400,000.        H. The ethylene-based copolymer of any of embodiments A-G,        wherein the ethylene-based copolymer has an intermolecular        composition distribution of about 15 wt. % or less.        I. The ethylene-based copolymer of any of embodiments A-H,        wherein the ethylene-based copolymer has an intramolecular        composition distribution of about 15 wt. % or less.        J. A masterbatch composition comprising the ethylene-based        copolymer of any of embodiments A-I.        K. The masterbatch composition of embodiment J, further        comprising at least one additive.        L. Method for modifying the rheology of a first composition        comprising the step of combining the ethylene-based copolymer of        any of embodiments A-I with the first composition.        M. A lubricating oil composition comprising:

(a) a lubricating oil base; and

(b) an ethylene-based copolymer comprising:

-   -   from about 35 wt. % to about 80 wt. % units derived from        ethylene, and    -   at least 1.0 wt. % of an α-olefin comonomer having 3 to 20        carbon atoms, based on the weight of the ethylene-based        copolymer,        wherein the ethylene-based copolymer has:

a melting point (Tm), as measured by DSC, of 80° C. or less;

a polydispersity index of about 2.8 or less; and

an intramolecular composition distribution of about 15 wt. % or less.

N. The lubricating oil composition of embodiment M, wherein thelubricating oil composition has a TE of about 2.2 or less.

O. The lubricating oil composition of embodiment M or N, wherein thelubricating oil composition has a TE of about 2.2 or less and theethylene-based copolymer comprises from about 35 wt. % to about 60 wt. %units derived from ethylene, based on the weight of the ethylene-basedcopolymer.P. The lubricating oil composition of any of embodiments M-O, whereinthe lubricating oil composition exhibits no substantial crystallinity atabout 0° C. or below.Q. The lubricating oil composition of any of embodiments M-P, whereinthe lubricating oil composition is characterized as having a slope lessthan one at less than 0° C. when viscosity at 0.1 rad/sec is plotted asa function of temperature.R. The lubricating oil composition of any of embodiments M-Q, whereinthe lubricating oil composition exhibits a SSI value of about 25 orless.S. The lubricating oil composition of any of embodiments M-R, whereinthe ethylene-based copolymer is substantially linear.T. The lubricating oil composition of any of embodiments M-S, whereinthe ethylene-based copolymer has a weight-average molecular weight (Mw)from about 80,000 to about 400,000.U. The lubricating oil composition of any of embodiments M-T, whereinthe lubricating oil composition comprises from about 0.1 wt. % to about5 wt. % of ethylene-based copolymer.V. The lubricating oil composition of any of embodiments M-U, furthercomprising at least one additive.W. The lubricating oil composition of any of embodiments M-V, furthercomprising from about 0.05 wt. % to about 5 wt. % pour point depressant,based on the weight of the lubricating oil composition.X. The lubricating oil composition of any of embodiments M-W, whereinthe lubricating oil composition is a crankcase lubricating oil,automatic transmission fluid, tractor fluid, hydraulic fluid, powersteering fluids, gear lubricant, or pump oil.Y. An ethylene-based copolymer comprising:

-   -   from about 35 wt. % to about 60 wt. % units derived from        ethylene; and    -   at least 1.0 wt. % or more of an α-olefin comonomer having 3 to        20 carbon atoms, based on the weight of the ethylene-based        copolymer,        wherein the ethylene-based copolymer:    -   is substantially amorphous; and    -   has a polydispersity index of about 2.8 or less.        Z. The ethylene-based copolymer of embodiment Y, wherein the        ethylene-based copolymer comprises from about 40 wt. % to about        50 wt. % unit derived from ethylene, based on the weight of the        ethylene-based copolymer.        AA. The ethylene-based copolymer of embodiment Y or Z, wherein        the ethylene-based copolymer has no substantial melting peak        when measured by DSC.        BB. The ethylene-based copolymer of any of embodiments Y-AA,        wherein the α-olefin comonomer is propylene, butene, hexene, or        octene.        CC. The ethylene-based copolymer of any of embodiments Y-BB,        wherein the ethylene-based copolymer is a ethylene/propylene        copolymer.        DD. The ethylene-based copolymer of any of embodiments Y-CC,        wherein the ethylene-based copolymer is a metallocene catalyzed        copolymer.        EE. The ethylene-based copolymer of any of embodiments Y-DD,        wherein the ethylene-based copolymer has an MFR (230° C., 2.16        kg) of from about 3 to about 10 kg/10 min.        FF. The ethylene-based copolymer of any of embodiments Y-EE,        wherein the ethylene-based copolymer has an intramolecular        composition distribution of about 15 wt. % or less.        GG. The ethylene-based copolymer of any of embodiments Y-FF,        wherein the ethylene-based copolymer has an intermolecular        composition distribution of about 15 wt. % or less.        HH. A masterbatch composition comprising the ethylene-based        copolymer of any of embodiments Y-GG.        II. The masterbatch composition of embodiment HH, further        comprising at least one additive.        JJ. Method for modifying the rheology of a first composition        comprising the step of combining the ethylene-based copolymer of        any of embodiments Y-GG with the first composition.        KK. A lubricating oil composition comprising:    -   (a) a lubricating oil base; and    -   (b) an ethylene-based copolymer comprising:        -   from about 35 wt. % to about 60 wt. % units derived from            ethylene, based on the weight of the ethylene-based            copolymer; and        -   at least 1.0 wt. % or more of an α-olefin comonomer having 3            to 20 carbon atoms,            wherein the ethylene-based copolymer:

is substantially amorphous; and

has a polydispersity index of about 2.8 or less.

LL. The lubricating oil composition of embodiment KK, wherein thelubricating oil composition has a TE of about 2.2 or less.

MM. The lubricating oil composition of embodiment KK or LL, wherein thelubricating oil composition has a TE of about 2.2 or less and theethylene-based copolymer comprises from about 40 wt. % to about 50 wt. %derived from ethylene, based on the weight of the ethylene-basedcopolymer.NN. The lubricating oil composition of any of embodiments KK-MM, whereinthe lubricating oil composition exhibits no substantial crystallinity atabout 0° C. or below.OO. The lubricating oil composition of any of embodiments KK-NN, whereinthe lubricating oil composition is characterized as having a slope lessthan one at less than 0° C. when viscosity at 0.1 rad/sec is plotted asa function of temperature.PP. The lubricating oil composition of any of embodiments KK-OO, whereinthe lubricating oil composition exhibits a SSI value of about 25 orless.QQ. The lubricating oil composition of any of embodiments KK-PP, whereinthe ethylene-based copolymer has no substantial melting peak whenmeasured by DSC.RR. The lubricating oil composition of any of embodiments KK-QQ, whereinthe ethylene-based copolymer has an MFR (230° C., 2.16 kg) of from about3 to about 10 kg/10 min.SS. The lubricating oil composition of any of embodiments KK-RR, whereinthe lubricating oil composition comprises from about 0.1 wt. % to about5 wt. % of ethylene-based copolymer.TT. The lubricating oil composition of any of embodiments KK-SS, furthercomprising at least one additive.UU. The lubricating oil composition of any of embodiments KK-TT, furthercomprising from about 0.05 wt. % to about 5 wt. % of a pour pointdepressant, based on the weight of the lubricating oil composition.VV. The lubricating oil composition of any of embodiments KK-UU, whereinthe lubricating oil composition is a crankcase lubricating oil,automatic transmission fluid, tractor fluid, hydraulic fluid, powersteering fluids, gear lubricant, or pump oil.WW. A method of making ethylene-based copolymers comprising the step ofcontacting ethylene monomers with one or more monomers with a solvent inthe presence of a catalyst in a reactor, under reactor conditionssuitable to produce an ethylene-based copolymer, wherein the resultingcopolymer comprises from about 40% to about 50 wt. % units derived fromethylene, and

a. has an MFR (230° C., 2.16 kg) of from about 3 to about 10 kg/10 min;

b. has a molecular weight distribution between about 2 and about 2.2;and

c. is substantially amorphous.

XX. The process of embodiment WW, wherein the copolymer is producedwithout the use of an additional shearing or degradation process.

YY. The process of embodiment WW or XX, further comprising the step ofextruding the copolymer into an aqueous bath to form polymer pellets.

ZZ. The process of any of embodiment YY, wherein the pellets have adiameter of at least about 3.0 mm and a ratio of length to diameter(L/D) of from about 1.1 to about 1.4.

AAA. The process of any of embodiments WW to ZZ, wherein the polymerpellets are free-flowing until a final packaging step.

BBB. The process of any of embodiments WW to AAA, further comprising apackaging step.

CCC. The process of embodiment BBB, wherein the packaging step comprisesbaling polymer pellets.

DDD. The process of embodiment BBB or CCC, wherein the packaging stepcomprises bagging the polymer pellets.

EEE. An ethylene-based copolymer comprising:

-   -   from about 35 wt. % to about 80 wt. % units derived from        ethylene, and    -   at least 1.0 wt. % or more of an α-olefin comonomer having 3 to        20 carbon atoms, based on the weight of the ethylene-based        copolymer,        wherein the ethylene-based copolymer has:    -   a melting peak (Tm), as measured by DSC, of 80° C. or less; and    -   a polydispersity index of about 2.8 or less;        and wherein at least 50 wt. %, at least 60 wt. %, at least 80        wt. %, at least 90 wt. %, or 100 wt. % of the ethylene-based        copolymers have an intermolecular composition distribution of        about 50 wt. % or less, or 40 wt. % or less, or 30 wt. % or        less, or 20 wt. % or less, or 15 wt. % or less, or 10 wt. % or        less, or 5 wt. % or less, and/or an intramolecular composition        distribution of about 50 wt. % or less, or 40 wt. % or less, or        30 wt. % or less, or 20 wt. % or less, or 15 wt. % or less, or        10 wt. % or less, or 5 wt. % or less.        FFF. Any one of embodiments A-M, P-KK, and NN-EEE, wherein the        copolymer has a polydispersity index of about 2.6 or less or 2.4        or less.

EXAMPLES

The following non-limiting embodiments identify exemplary ethylene-basedcopolymers, properties thereof, and uses thereof.

Preparation of Ethylene-Based Copolymers; Propylene Comonomers

A polymer composition was synthesized in one continuous stirred tankreactor. The polymerization was performed in solution, using hexane as asolvent. In the reactor, polymerization was performed at a temperatureof 90° C., an overall pressure of 20 bar and ethylene and propylene feedrates of 1.3 kg/hr and 2 kg/hr, respectively. As the catalyst system,N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate was used toactivatedi(p-triethylsilylphenyl)methenyl[(cyclopentadienyl)(2,7-di-tert-butylfluoren-9-yl)]hafniumdimethyl. In the process, hydrogen addition and temperature control wereused to achieve the desired MFR. The catalyst, activated externally tothe reactor, was added as needed in amounts effective to maintain thetarget polymerization temperature.

The copolymer solution emerging from the reactor was stopped fromfurther polymerization by addition of water and then devolatilized usingconventionally known devolatilization methods such as flashing or liquidphase separation, first by removing the bulk of the hexane to provide aconcentrated solution, and then by stripping the remainder of thesolvent in anhydrous conditions using a devolatilizer or a twin screwdevolatilizing extruder so as to end up with a molten polymercomposition containing less than 0.5 wt. % of solvent and othervolatiles. The molten polymer was cooled until solid.

Preparation of Lubricant Oil Composition

The ethylene propylene copolymer from Example 1 was dissolved in STSENJ102 oil available form ExxonMobil at a 1.5 wt. % concentration, toresemble commercially used lubricant formulations.

Preparation of a Lubricant Oil Concentrate

A lubricant oil concentrate was prepared with 11.3 wt. % of the ethylenepropylene copolymer of Example 1, 14.8 wt. % of a detergent inhibitorpackage, 0.3 wt. % of a pour point depressant, and the remainder is aSAE 10W40 base oil. The base oil was composed of 58 wt. % of Chevron 100and 42 wt. % of Chevron 220 oils available from Chevron.

The following examples demonstrate that ethylene-based copolymersdescribed herein are useful as components of lubricant oil compositionshaving properties similar to those of formulations made from componentsprepared by more complex and more expensive multi-step methods.

Group I Examples Example 1 Ethylene Propylene Polymers at about 45% C₂Composition

As shown in Table 2 and FIG. 1, ethylene-based copolymers were preparedaccording to the procedure outlined above and tested for TE in AmericanCore 150N base oil and as a 1% solution in the same base oil for the SSIdetermination.

TABLE 2 MFR MFRR % C₂ TE SSI (30 pass KO) Example 1.1 6.27 30.74 45.61.86 27.3 Example 1.2 6.27 30.74 45.4 1.88 25.5 Example 1.3 6.16 29.8745.6 1.89 25.2 Example 1.4 6.16 29.87 45.6 1.91 26.0 Example 1.5 6.6632.36 44.6 1.93 29.1 Example 1.6 6.66 32.36 44.6 1.87 24.4 Example 1.75.99 30.23 44.4 1.87 27.4 Example 1.8 5.99 30.23 44.4 1.88 25.4 Example1.9 5.99 30.23 44.4 1.89 25.8 Example 1.10 5.33 30.66 44.4 1.93 30.2Example 1.11 5.33 30.66 44.4 1.93 27.2 Example 1.12 5.33 30.66 44.3 1.9326.9 Example 1.13 5.00 31.63 45.2 2.00 29.3

Example 2 Ethylene Propylene Polymers Near 45% C₂ Composition

Ethylene-based copolymers were made according to the procedure outlinedabove and tested for TE in American Core 150N base oil and as a 1%solution in the same base oil for the SSI determination.

TABLE 3 SSI C₂ (30 pass Example content MFR KO) TE Mw Mn MWD 2.1 48.45.78 25.97 1.98 76177 35779 2.13 2.2 48.2 6.81 27.02 1.97 76093 354892.14 2.3 48.0 6.72 27.32 1.96 73644 35037 2.1 2.4 47.2 26.07 1.91 7175632086 2.23 2.5 47.2 7.8 25.56 1.90 71573 33309 2.15 2.6 48.2 6.7 27.531.90 75120 35801 2.1 2.7 51.2 3.32 32.44 2.12 85268 40269 2.12

Example 3 Range of Ethylene Propylene Polymers Composition

Ethylene-based copolymers were made according to the procedure outlinedabove and tested for TE in American Core 150N base oil and as a 1%solution in the same base oil for the SSI determination.

TABLE 4 KV100 SSI EPR 1% EPR (30 M_(W) MFR @ Polymer in pass Example(g/mol) 230° C. Wt. % C₂ AC150 TE KO) 3.1 97,000 3.6 74.4 12 2.46 26.283.2 80,000 8.4 71.8 11.12 2.14 18.99 3.3 89,000 5.6 71.8 11.57 2.3023.04 3.4 99,000 3.8 71.9 11.75 2.42 27.25 3.5 103,000 2.5 70.9 12.692.52 29.81 3.6 110,000 2.3 68.2 13.13 2.55 31.80 3.7 95,000 4.9 64.111.22 2.32 25.77 3.8 109,000 3.3 60.6 12.27 2.39 30.09 3.9 98,000 6.654.0 11.28 2.240 3.10 108,000 4.6 51.5 11.65 2.334 3.11 85,100 3.3978.32 3.12 110,800 1.5 74.1 13.23 2.69 31.91 3.13 57,000 14.9 73.1 9.5521.76 9.90 3.14 44,200 88.0 73.7 8.475 1.43 3.49 3.15 36,600 203.0 73.47.848 1.19 3.00 3.16 57,300 18.5 62.1 9.021 1.64 10.13 3.17 101,300 2.465.3 12.16 2.47 29.41 3.18 87,100 6.1 60.7 10.9 2.12 23.81 3.19 67,1007.4 77.9 10.52 1.58 6.99 3.20 45,800 40.0 67.7 8.514 2.69 31.91 3.2152,800 27.3 68.9 8.966 1.76 9.90 3.22 97,600 6.3 44 10.52 2.039 3.3398,700 8.7 41.3 9.988 1.889 3.34 76,800 8.9 47.4 9.718 1.810 3.35109,000 11.51 2.299 3.36 125,000 12.57 2.553 3.37 89,600 3.1 70.2 11.5123.89 2.28 3.38 71,100 7.7 69.7 10.38 16.79 2.00 3.39 77,200 9.1 59.810.15 19.14 1.95 3.40 69,800 10.1 61.1 9.85 15.81 1.86 3.41 62,800 12.962.1 9.488 12.35 1.75

TABLE 5 Comparative example of commercial viscosity modifier C₂ wt. % TESSI PTN 8900 64.50 2.00 24

Group II Examples Amorphous Ethylene-Based Copolymers

Lubricant oil compositions composed of amorphous ethylene-basedcopolymers were prepared and compared to compositions described in U.S.Pat. No. 6,589,920.

Preparation of an Ethylene-Based Copolymer; Propylene Comonomers

A polymer composition is synthesized in one continuous stirred tankreactor. The polymerization is performed in solution, using hexane as asolvent. In the reactor, polymerization is performed at a temperature of90° C., an overall pressure of 20 bar and ethylene and propylene feedrates of 1.3 kg/hr and 2 kg/hr, respectively. As the catalyst system,N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate is used toactivatedi(p-triethylsilylphenyl)methenyl[(cyclopentadienyl)(2,7-di-tert-butylfluoren-9-yl)]hafniumdimethyl. In the process, hydrogen addition and temperature control isused to achieve the desired MFR. The catalyst, activated externally tothe reactor, is added as needed in amounts effective to maintain thetarget polymerization temperature.

The copolymer solution emerging from the reactor is stopped from furtherpolymerization by addition of water and then devolatilized usingconventionally known devolatilization methods such as flashing or liquidphase separation, first by removing the bulk of the hexane to provide aconcentrated solution, and then by stripping the remainder of thesolvent in anhydrous conditions using a devolatilizer or a twin screwdevolatilizing extruder so as to end up with a molten polymercomposition containing less than 0.5 wt % of solvent and othervolatiles. The molten polymer is cooled until solid.

Preparation of Lubricant Oil Composition

The ethylene propylene copolymer from above is dissolved in STS ENJ102oil available from ExxonMobil at a 1.5 wt. % concentration, to resemblecommercially used lubricant formulations. The solution TE and SSI aremeasured and compared to a similar solution of Paratone® 8900 which is acommercially available viscosity improver which is made by separatesolution and devolatilization of different ethylene-propylene copolymerfractions followed by blending and visbreaking in a twin screw extruder.

As shown in Table 6(b), at similar ethylene content the presentlubricant oil compositions will not exhibit a DSC peak, while providingdesirable TE and SSI properties.

TABLE 6(a) Ethylene (wt. %) DSC, ° C. ‘920 patent ex. 6 47.2 −38.5 ‘920patent ex. 7 46.8 −36.2 ‘920 patent ex. 8 49.6 −40.8

TABLE 6(b) Shear MFR Ethylene Thickening Stability (g/10 min) (wt. %)DSC, ° C. Efficiency Index Ex. 1 7.8 47.0 None detected 1.81 25 Ex. 26.72 48.0 None detected 1.85 25 Ex. 3 5.87 48.2 None detected 1.89 25

Additional samples were prepared according to the techniques describedin “II. Examples”. As shown in Table 7 and FIG. 3, these samples werethen analyzed for physical properties and compared to conventionalmaterials.

TABLE 7 Polymer C₂ Crystallinity MFR 001 48.4 0 5.78 — 002 48.3 0 — 00348.2 0 6.81 — 004 48 0 6.72 — 005 48 0 — 006 47.2 0 — 007 47.2 0 7.8 —008 48.2 0 6.7 — 009 50.6 1.7 4.02 comparative 010 51.2 2.9 3.32comparative 011 53.2 5.9 2.37 comparative 012 54.7 7.8 1.83 comparative013 57.8 11.3 comparative ref sample 55 8.5 comparative

Additional properties are shown in Tables 8-10:

TABLE 8 Polymer Mw Mn MWD 001 76177 35779 2.13 003 76093 35489 2.14 00473644 35037 2.1 006 71756 32086 2.23 007 71573 33309 2.15 008 7512035801 2.1 010 85268 40269 2.12 (comparative)

TABLE 9 DSC Example crystallinity C₂ MFR MFRR 1.1 0 46.6 5.1 32 1.2 045.7 5.7 30 1.3 0 44.8 7.1 29 1.4 0 44.8 7.5 29 1.5 0 44.8 7.0 29 1.6 044.9 7.1 29

TABLE 10 Example MFR C₂ 2.1 7.73 44.20 2.2 6.81 44.90 2.3 5.90 45.40 2.45.79 45.80 2.5 6.08 45.90 2.6 6.25 45.80 2.7 5.93 45.80 2.8 6.18 45.502.9 6.22 45.50 2.10 6.47 45.30 2.11 6.25 45.30 2.12 6.33 45.40 2.13 6.4845.40 2.14 6.54 45.50 2.15 6.02 45.50 2.16 5.51 45.80 2.17 5.32 45.702.18 5.63 45.80 2.19 5.85 45.60 2.20 6.14 45.30 2.21 6.07 45.30 2.226.17 45.30 2.23 6.25 45.20 2.24 5.13 44.70 2.25 5.40 44.80 2.26 5.6444.70 2.27 5.47 44.50 2.28 6.69 44.00 2.29 6.83 44.30 2.30 6.92 44.202.31 6.55 44.20 2.32 7.40 44.20 2.33 7.42 44.30

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.All references, patents and documents described herein are incorporatedby reference herein, including any priority documents and/or testingprocedures to the extent they are not inconsistent with this text. As isapparent from the foregoing general description and the specificembodiments, while forms of the invention have been illustrated anddescribed, various modifications can be made without departing from thespirit and scope of the invention. Accordingly, it is not intended thatthe invention be limited thereby.

1. A copolymer comprising: from about 35 wt. % to about 80 wt. % unitsderived from ethylene, and at least 1.0 wt. % of units derived fromα-olefin comonomer having 3 to 20 carbon atoms, based on the weight ofthe copolymer, wherein the copolymer has: a melting peak (Tm), asmeasured by DSC, of 80° C. or less; a polydispersity index of about 2.8or less; and has an intramolecular composition distribution of about 15wt. % or less.
 2. The copolymer of claim 1, wherein the copolymer has apolydispersity index of about 2.4 or less.
 3. The copolymer of claim 1,wherein at least 80 wt. % of the copolymer has an intermolecularcomposition distribution of about 50 wt. % or less.
 4. The copolymer ofclaim 1, wherein the copolymer has an intramolecular compositiondistribution of about 15 wt. % or less.
 5. The copolymer of claim 1,wherein the copolymer is substantially linear.
 6. The copolymer of claim1, wherein the copolymer comprises from about 40 wt. % to about 60 wt. %units derived from ethylene, based on the weight of the copolymer. 7.The copolymer of claim 1, wherein the α-olefin comonomer is propylene,butene, hexene, or octene.
 8. The copolymer of claim 1, wherein thecopolymer has a weight-average molecular weight (Mw) of from about80,000 to about 400,000.
 9. A composition comprising the copolymer ofclaim 1 and at least one additive.
 10. Method for modifying the rheologyof a first composition comprising the step of combining the copolymer ofclaim 1 with the first composition.
 11. A lubricating oil compositioncomprising a lubricating oil base and the copolymer of claim
 1. 12. Thelubricating oil composition of claim 11, wherein the lubricating oilcomposition has at least one of: (a) a thickening efficiency of about2.2 or less; (b) a slope less than one at less than 0° C. when viscosityat 0.1 rad/sec is plotted as a function of temperature; and (c) a shearstability index value of about 25 or less.
 13. The lubricating oilcomposition of claim 11, wherein the lubricating oil compositionexhibits no substantial crystallinity at about 0° C. or below.
 14. Thelubricating oil composition of claim 11, wherein the lubricating oilcomposition comprises from about 0.1 wt. % to about 5 wt. % ofcopolymer.
 15. The lubricating oil composition of claim 11, furthercomprising from about 0.05 wt. % to about 5 wt. % pour point depressant,based on the weight of the lubricating oil composition.
 16. Anethylene-based copolymer comprising: from about 35 wt. % to about 80 wt.% units derived from ethylene, and at least 1.0 wt. % or more of anα-olefin comonomer having 3 to 20 carbon atoms, based on the weight ofthe ethylene-based copolymer, wherein the ethylene-based copolymer has:a melting peak (Tm), as measured by DSC, of 80° C. or less; and apolydispersity index of about 2.8 or less; and wherein at least 60 wt. %of the copolymer has an intermolecular composition distribution of about50 wt. % or less and/or an intramolecular composition distribution ofabout 50 wt. % or less.